Aqueous polyester coating composition

ABSTRACT

An aqueous coating composition containing in admixture a water soluble polyester, a water soluble orthoamic acid diamine and minor amounts of other water soluble polymeric coating materials. The water soluble orthoamic acid diamine is prepared by reacting in a suitable solvent for at least one reactant, an aromatic diamine and an aromatic dianhydride with the reactants in the molar ratio of m/(m-1) respectively, where m has a value between 2 and about 7. The diamine is dissolved in a solvent and the dianhydride is slowly added to the solution to form the orthoamic acid diamine. The reaction is carried out at a temperature below that at which imidization occurs. The reaction product may then be made water soluble by the addition of a volatile base such as ammonia or a volatile amine. Water solutions of polyester resins and the orthoamic acid diamine are utilized to produce coatings on substrates such as magnet wire. Water soluble phenol-formaldehyde resins, aminoplasts, epoxy resins and the like, and accelerators and other ingredients may be added to the coating solution. Coatings produced on substrates, including magnet wire, may be heat cured to form clear, tough, flexible, adherent solvent resistant dielectric thermally stable coatings.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending applicationSer. No. 475,483, filed June 3, 1974, by Marvin A. Peterson, for"Coating Composition and Method of Coating Substrates Therewith", whichapplication Ser. No. 475,483, is a continuation-in-part of co-pendingapplication Ser. No. 467,615, filed May 6, 1974, by Marvin A. Peterson,for "Process and Composition for Producing Coating Material," whichapplication Ser. No. 467,615, is co-pending with this application and acontinuation of co-pending application Ser. No. 822,899, filed May 8,1969, by Marvin A. Peterson, for "Improved Process for Producing WireCoatings From Prepolymeric Materials," now abandoned.

FIELD OF THE INVENTION

The present invention relates to coating compositions for producingpolymeric coatings on substrates, and more particularly to aqueous basedpolymeric coating solutions contaning water soluble polyesters orpolyesterimides, or mixtures thereof, in admixture with orthoamic aciddiamines. More specifically, the invention relates to a coatingcomposition, a process for producing coating compositions of theforegoing character, a process of coating substrates therewith, coatingsproduced thereby, and to coated substrates. Coatings produced from theaqueous based polymeric coating solutions find particular but notnecessarily exclusive utility in applications requiring electrical gradeproperties, including high thermal stability, dielectric strength andcut-through temperature, are curable in conventional wire towerapparatus, and are suitable for overcoating with materials such asNylon.

BACKGROUND OF THE INVENTION

A wide variety of synthetic resins have been developed for use aselectrical insulating material, particularly material which issatisfactory for use as slot insulation in dynamoelectric machines andfor use as insulation for conductors which are to be employed as magnetwires (insulated electrical conductors) in electrical apparatus. It iswell known that insulating material which is to be employed for thesepurposes must be able to withstand extremes of mechanical, chemical,electrical and thermal stresses. Thus, wires to be employed as coilwindings in electrical apparatus are generally assembled on automatic orsemi-automatic coil winding machines which, by their very nature, bend,twist, stretch and compress the enameled wire in their operation. Afterthe coils are wound, it is common practice to coat them with a varnishsolution containing solvents such as ketones, alcohols, phenols andsubstituted phenols, aliphatic and aromatic hydrocarbons, halogenatedcarbon compounds, and the like. Insulating coatings on magnet wire mustbe resistant to these solvents.

In order to converse space in electrical apparatus, it is essential thatthe individual turns which make up the coils be maintained in closeproximity to each other. Because of the closeness of the turns, and thefact that there may be a large potential gradient between adjacentturns, it is necessary that the coating resins employed as wire enamelshave a high dielectric strength to prevent short circuiting betweenadjacent coils. In operation of electrical apparatus containing coiledwires, high temperatures are often encountered and the enamels must beable to withstand these high temperatures as well as the mechanicalstresses and vibrations encountered in electrical apparatus so that theenamel coating does not soften or come off the wire.

It is also well known that the power output of motors and generators canbe increased a great deal by increasing the current density in themagnet wires of these machines. However, increasing the current densitythrough magnet wires is accompanied by an attendant rise in theoperating temperature of the magnet wires. This increased temperaturehas meant that conventional water based organic enamels, particularlythe economically attractive polyester based resins, could not be used inhigh current density windings because the higher operating temperaturesencountered caused deterioration or decomposition of the enamel coating.

In the past, many attempts have been made to prepare magnet wires whichmet all of the mechanical, chemical, electrical and thermal requirementsof high temperature magnet wire while still being economically feasible.Cost per unit of power output of a resulting dynamoelectric machine is avery important factor in any magnet wire insulation, since an excessivemagnet wire cost tends to make a magnet wire impractical for useregardless of its properties. While excessive cost of a magnet wire isgenerally the result of five factors, a sixth factor, that of ecologyand environmental considerations in connection with the use of organicsolvents, is now of prime importance.

The first, and the most obvious, factor is the cost of the raw materialsin the resin which is to be applied to the conductor. The second factoris related to the ability of the resinous material to be dissolved inreadily available, inexpensive solvents. Since resinous materials arepreferably stored and transported in solution, the bulk and weight ofthe solvent play a large part in the cost of having the resin at theplace where it is to be used at the time it is to be used. In practice,it has been found that it is desirable to employ resinous materials aswire enamels which are capable of being held in solutions which containat least 30 to 50 percent, by weight, of solids. Since the solvents inthe resinous solution are generally allowed to escape without recoveryfrom the wire coating operation, the cost of the solvent is an importantfactor in the cost of the cured enamel.

The third factor which vitally affects the cost of an enameled wire isthe time required to cure the enamel once it has been applied to theconductor. If this time is excessive, an unduly large baking oven isrequired or the speed of the wire through the oven must be maintained atan uneconomically low rate. The fourth factor which affects the cost ofmagnet wire is the flexibility of the conditions which may be employedin applying the resin to the conductors and in curing the resin once ithas been applied. If the wire speed range in the curing operation, thecuring temperature, and the wire diameter sizes are critical, it isobvious that a large amount of defective magnet wire may be preparedunder mass production conditions; however, if large variations in curingconditions are tolerable, only a very small amount of the magnet wireprepared need be discarded because of defective insulation.

The fifth factor which is important in the cost of magnet wire is theability of the same resinous solution to be applied to both round andrectangular conductors and to conductors made of various metals. Ifdifferent resin solutions must be used for each type of conductor, thetime required to change the resin solution is an integral part of themagnet wire cost.

The sixth factor, which is important to the overall production process,as well as to the environment in which the production takes place, isthe ecological and pollution factor, and the related safety and toxicityconsiderations. Organic solvents are becoming increasingly valuable, andproduction communities are becoming moe concerned about the quality oflife and the environment surrounding the manufacturing operation. Thus,it is highly important for a variety of reasons to avoid discharging andwasting organic solvents directly into the atmosphere. A relatedconsideration with respect to the use of organic solvents is thereforethe cost of handling and disposal. It has been established that for atypical organic solvent coating operation in a conventional wire tower,more than 90% of the fuel bill is utilized to heat air to diluteevaporated solvent and thereby dilute it to a nonflammable state and toburn the offgases to CO₂ and H₂ O before they are emitted into theatmosphere.

At the present time, commercially available coating materials for use inelectrical applications, such as the coating materials disclosed in U.S.Pat. No. 2,936,296, issued May 10, 1960, to F.M. Precopio and P.W. Foxfor "Polyesters From Terephthalic Acid, Ethylene Glycol and a HigherPolyfunctional Alcohol," and used and sold commercially under thetrademark "ALKANEX" by General Electric Company, are widely used, highlysuccessful and effective compositions, but have the economic andecological disadvantage of requiring the use of organic solvents. Whereorganic solvents are used, they are driven off during curing of thecoatings and are generally not economically recoverable. Many suchsolvents are becoming economically, ecologically and environmentallyprohibitive, making it increasingly desirable to utilize substantiallywater based solvents.

A wide variety of aqueous polyesters coating solutions are known in theart. With few exceptions, however, the coatings produced from suchaqueous solutions are not suitable for electrical applications,particularly for wire enamels. Polyester coatings from aqueous solutionscure only very slowly to a tack-free state, exhibit excessive weightloss on curing as compared to organic solvent based resins, and, onaging, become brittle, darken, lose flexibility and generallydepolymerize under the conditions of most electrical applications.

Polyamide and polyimide coating materials in aqueous solutions, andcoatings produced therefrom, are generally well known in the art, andare highly effective for producing stable electrical grade coatings.See, for example, U.S. Pat. No. 3,652,500, issued Mar. 28, 1972, to M.A.Peterson, for "Process for Producing Polyamide Coating Materials By EndCapping"; U.S. Pat. No. 3,663,510, issued May 16, 1972, to M.A.Peterson, for "Process for Producing Polyamide Coating Materials"; U.S.Pat. No. 3,507,765, issued Apr. 21, 1970, to F.F. Holub and M.A.Peterson, for "Method For Electrocoating A Polyamide Acid"; U.S. Pat.No. 3,179,614, issued Apr. 20, 1965, to W.M. Edwards, for "PolyamideAcids, Compositions Thereof, And Process For Their Preparation"; U.S,Pat. No. 3,179,634, issued Apr. 20, 1965, to W.M. Edwards, for "AromaticPolyimides And The Process for Preparing Them"; and U.S. Pat. No.3,190,856, issued June 22, 1965, to E. Lavin, et al. for "PolyamidesFrom Benzophenonetetracarboxylic Acids And A Primary Diamine." The priorart involves generally the preparation of a coating medium containing ahigh molecular weight polyamide acid, and application of the coatingmedium to a substrate to provide a polyamide acid coating thereon,followed by the curing of the high molecular weight polyamide acid to apolyimide. While such coating materials produce coatings havingdesirable properties, particularly for electrical applications, they arerelatively more expensive than polyester type coating materials.

Aqueous base polyamide acid systems, as described in the above-mentionedpatents to Peterson, result in excellent high temperature, electricalgrade coatings (250° C., 40,000 hr., insulation coatings), which arestable, and easily made and used, but are relatively expensive whencompared to the polyester compositions. It should be noted that thepolyester (Alkanex type) magnet wire coating provides a thermalinsulation barrier which, though it is less than that of polyimidemagnet wire coating, nevertheless is highly suitable for a large segmentof the magnet wire needs in the industry, particularly for class Bapplications, (135° C., 20,000 hr. coatings).

Aqueous based acrylic systems, of the type described in U.S. Pat. No.2,787,603, issued Apr. 2, 1957, to P.F. Sanders for "Aqueous CoatingCompositions and Substrates Coated Therewith," while inexpensive, arenot generally suitable for high temperature electrical grade coatingsapplications such as class B applications. Moreover, such aqueous basedacrylic systems are emulsions and not solutions, thereby creatingcertain stability problems.

Efforts have been made to mix various emulsion polymerized resins toupgrade coatings produced therefrom. For example, properties of coatingsand films from polyacrylic polyester resins in aqueous solvents havebeen somewhat improved by the addition of water solublephenol-formaldehyde resins, epoxy resins and melamine resins. Suchpolymer blends, however, are generally not sufficiently upgraded to theclassical polyester grade insulations presently utilized in the magnetwire industry.

Because of the high latent heat of vaporization of water, it isdesirable in water based systems, particularly for application as wireenamels, to utilize as high a solids content as is possible,commensurate with workable viscosities, when the medium is used withautomatic coating apparatus such as wire towers. High molecular weightpolymers, such as the polyamide acid polymers which are described in thepatents listed above, produce extremely viscous solutions except inrelatively low solids content systems. For many applications, the lowsolids content systems are quite suitable. For wire tower use, however,the low solids content aqueous solution creates production problemswhich reduces the efficiency of the tower.

Criteria for electrical insulating materials, such as magnet wireinsulations, slot insulations, insulating varnishes and the like havebeen established in the art. In order to determine whether theinsulation on a magnet wire will withstand the mechanical, chemical,electrical and thermal stresses encountered in winding machines andelectrical apparatus, it is customary to apply the resin to a conductor,by a method which will be described hereinafter, and to subject theenameled wire to a series of tests which have been designed to measurethe various properties of the enamel on the wire.

Various tests, which will be described in detail later, include theabrasion resistance tests, the 25 percent elongation plus 3X flexibilitytest, the snap elongation test, the 70-30 solvent resistance test, the50-50 solvent resistance test, the dielectric strength tests, theflexibility after heat aging test, the heat shock test, the cut-throughtemperature test, and the high temperature dielectric strength losstest. The enamel on a conductor which will withstand the mechanical,chemical and electrical stresses encountered in magnet wire applicationsand which is operable at temperatures of at least 135° C. for extendedperiods of time must withstand at least 10 strokes with the average ofthree tests being not less than 20 in the repeated scrape abrasionresistance test, must withstand 980 "grams to fail" in theunidirectional scrape resistance test, must pass the 25 percentelongation plus 3X flexibility test, must show no surface defects in thesnap test, must show no attack on the insulation in either of thesolvent resistance tests, must have a dielectric strength of at least1500 v. per mil twisted pair, must show no surface defects when wound ona 3X mandrel after heat aging for 100 hours at 175° C., must show nodefects when a 5X coil is aged for 30 minutes at 155° C. in the heatshock test, and must have a cut-through temperature of at least 215° C.under a 1000 gram load for 18 AWG heavy coated insulated magnet wire oncopper conductor. In addition, for the same type of magnet wire withNylon overcoat the insulated conductor must not show a loss indielectric strength of more than 2/3 of original dielectric strength ora minimum of 1500 volts per mil twisted pair, must show no surfacedefects when a 3X coil is aged for 30 minutes at 155° C in the heatshock test, and must have a cut-through temperature of at least 200° Cunder a 1000 gram load.

The abrasion resistance tests, flexibility test, and snap test areemployed to determine the mechanical properties of a magnet wire.Abrasion resistance is a measure of the amount of abrasion an insulatedelectrical conductor will withstand before the insulating enamel is wornaway from the conductor. Repeated scrap abrasion resistance is measuredby rubbing the side of a loaded round steel needle back and forth acrossthe surface of an insulated electrical conductor until the enamel isworn away. The number of strokes required to wear the enamel away isreferred to as the number of abrasion resistance strokes. Unidirectionalscrape resistance is measured by rubbing the side of a round steelneedle across the surface of an insulated electrical conductor underincreasing load until the conductor is exposed. The load required toexpose the conductor is referred to as the "grams-to-fail" load. For acomplete description of the procedure followed in abrasion resistancetesting where a needle is rubbed back and fourth across the insulatedelectrical conductor, reference is made to NEMA Standard Section MW 24which describes the procedure followed in the present invention. ThisNEMA Standard is incorporated by reference into the present application.

The flexibility of the enamel on a magnet wire is determined bystretching the enameled conductor and examining the stretched portion ofthe wire under a binocular microscope at a magnification of ten todetermine if there are any imperfections on the surface of the enamel.The imperfections which may be noted on the surface of the enamel are aseries of parallel surface lines of fissures which are perpendicular tothe long axis of the wire. This condition of the enamel film is known ascrazing. Another defect which can sometimes be observed is a break inthe enamel film in which the two sections of the film are actuallyphysically separated and the opening extends in depth to the exposedconductor. This defect is called a crack. A third defect which may benoted is a mar or blemish in the enamel film.

In the 25 percent elongation plus 3X flexibility test an insulatedelectrical conductor having a diameter X is elongated 25 percent andwound about a mandrel having a diameter 3X. If examination of the enamelunder a magnification of ten shows none of the surface defects notedabove, the insulation on the conductor passes this flexibility test. Insome of the examples which follow, flexibility tests using elongationsother than 25 percent and mandrels having a diameter other than 3X areemployed. However, in all of these cases the flexibility test is assevere as the 25 percent elongation plus 3X flexibility test.

The snap elongation test measures the ability of the insulation towithstand a sudden stretch to the breaking point of the conductor. Theinsulation on the conductor must not show any cracks or tubing beyondthree test wire diameters on each side of the fracture after theinsulated conductor is jerked to the breaking point at the rate of 12 to16 feet per second.

Solvent resistance tests are conducted to determine whether a magnetwire will satisfactorily withstand the chemical stresses found inelectrical applications, i.e., whether the enamel is resistant to thesolvents commonly employed in varnishes which may be used as an overcoatfor the enameled wires. The solvent resistance test is the determinationof the physical appearance of an enameled wire after immersion in arefluxing bath of a specified solution. Two solution systems are usedfor each sample of wire. Both of these solutions contain a mixture ofalcohol and toluene. The alcoholic portion is composed of 100 parts byvolume of U.S.P. ethanol and 5 parts by volume of C.P. methanol. Onesolvent test solution (which is designated as 50-50) consists of equalparts by volume of the above alcohol mixture and of toluene. The secondsolution (which is designated as 70-30) is 70 parts of the alcoholmixture and 30 parts of toluene.

In the usual operation of the test, about 250 ml. of the solution isplaced in a 500 ml. round-bottomed, single-necked flask which is heatedby a suitable electrical heating mantle. A reflux condenser is attachedto the flask and the solution is maintained at reflux temperature. Asample is formed so that three or more straight lengths of the wirehaving cut ends can be inserted through the condenser into the boilingsolvent. After five minutes the wire is removed and examined forblisters, swelling or softening. Any visible change in the surfaceconstitutes a failure. Soft (requiring the thumbnail to remove it) butsmooth and adherent enamel is considered to pass this five minutes test.The samples are then returned to the solvent for another five minutesand re-examined for the same defects. If the enamel shows any blistersor swelling at the end of either the five minutes or the ten minutestest in the 70-30 solution (the 70-30 solvent resistance test) theenamel has failed the solvent resistance test. If the enamel shows anyblisters or swelling at the end of the five minutes test in the 50-50mixture (the 50--50 solvent resistance test) the enamel has failed thissolvent resistance test.

The dielectric strength of the enamel film determines whether theinsulation on a magnet wire can withstand the electrical stressesencountered in electrical apparatus. The dielectric strength of aninsulating film is the voltage required to pass a finite current throughthe film. In general, dielectric strength is measured by increasing thepotential across the insulating film at a rate of 500 volts per secondand taking the root mean square of the voltage at which the finitecurrent flows through the film as the dielectric strength.

The type of specimen employed to measure dielectric strength is a samplemade up of two pieces of enameled wire which have been twisted togethera specified number of times while held under a specific tension. Aportential is then placed across the two conductors and the voltage isincreased at the rate of 500 volts per second until a finite currentflows through the insulation. The voltage determined by this method isreferred to as "dielectric strength, volts (or volts per mil), twistedpair." The number of twists and the tension applied to the twisted wireis determined by the size of the bare conductor. A complete listing ofthe specifications for various wire sizes are described in theaforementioned NEMA Standard Section MW 24.

In order to determine whether a magnet wire may be employed at hightemperatures, it is necessary to measure properties of the enameledconductor at high temperatures. Among the properties which must bemeasured are the cutthrough temperature of the enamel, the flexibilityof the enamel after heat aging at an elevated temperature, the heatshock characteristics of the enamel, and the dielectric strength loss ofthe enamel when heated at high temperatures in air. Since it is wellknown that copper is the most common conductor, all of the thermal testsof magnet wire are conducted on copper magnet wire.

The cut-through temperature of the enamel film is measured to determinewhether the insulation on a magnet wire will flow when the wire israised to an elevated temperature under compressive stress. Thecut-through temperature is the temperature at which the enamel filmseparating two magnet wires, crossed at 90° and supporting a given loadon the upper wire, flows sufficiently to establish electrical contactbetween the two conductors. Since magnet wires in electrical apparatusmay be under compression, it is important that the wires be resistant tosoftening by high temperature so as to prevent short circuits within theapparatus. The tests are conducted by placing two eight inch lengths ofenameled wire perpendicular to each other under a load of 1000 grams atthe intersection of the two wires. A potential of 110 volts A.C. isapplied to the end of each wire and a circuit which contains a suitableindicator such as a line recorder, a buzzer or neon lamp is establishedbetween the ends of the wires. The temperature of the crossed wires andthe load is then increased at the rate of 3° per minute until the enamelsoftens sufficiently so that the bare conductors come into contact witheach other and cause the indicator to signal a failure. The temperatureat which this circuit is established is measured by a thermocoupleextending into a thermowell to a point directly under the crossed wires.The cut-through temperature is taken as the temperature in thethermowell at the moment when the current first flows through thecrossed wires. Although this temperature is always somewhat lower thanthe true temperature of the wires, it gives a fairly accuratemeasurement of the cut-through temperature range of the enameled wirebeing tested. Magnet wires designated for operating temperatures of atleast 135° C. should have a cut-through temperature of at least 175° C.

When measuring properties of an insulating film such as percentelongation after heat aging, heat shock, weight loss after heating invacuum, and dielectric strength loss after heating in air, what isactually being measured is the effect of thermal degradation of theenamel on the particular properties being measured. The moststraightforward method of measuring this thermal degradation of anenamel on a wire is to maintain the enameled wire at the temperature atwhich it is desired to operate the wire until decomposition takes place.

However, this method is impractical in the evaluation of new materialsbecause of the relatively long periods of time involved. Thus, it mightbe found that an enameled wire may operate successfully at a temperatureof 135° C., for example, for five to ten years before any substantialthermal degradation takes place. Because it is obviously impractical towait such a long period of time to find out whether a resin issatisfactory for magnet wire enamel, it is customary to conductaccelerated heat life tests on these enameled wires. Since thermodynamictheories show that the rate of a given reaction can be determined as afunction of temperature, it is possible to select elevated temperaturesfor thermal tests of enamel films and to calculate the thermalproperties of the enameled wire at the desired operating temperaturefrom these accelerated test data. Although it might be expected thatdegradation reactions which occur at elevated test temperatures mightnot occur at temperatures at which the magnet wire is to be operatedbecause of activation energies required to initiate certain reactions,experience has shown that accelerated heat life tests are an accuratemethod for determining the heat life of a material at operatingtemperatures.

In determining whether an enamel film will lose its flexibility afterextended periods of time at operating temperature, it is customary toheat age a sample of the enameled wire. In practice it has been foundthat for a magnet wire to be satisfactory for use in dynamoelectricmachines at temperatures of at least 135° C. a sample of the enameledwire having a conductor diameter X must show no surface defects whenwound on a mandrel having a diameter of 3X after heat aging for 100hours in a circulating air oven maintained at a temperature of 175° C.

The effect of high temperatures on the flexibility of a magnet wireenamel may also be measured by winding a sample of the enameled wirehaving a conductor diameter X on a mandrel having a diameter of 5X,removing the sample of wire from the mandrel and placing it in acirculating air oven maintained at 155° C. After 30 minutes the sampleof wire should show no surface defects in any of the windings in orderfor the enameled wire to have sufficient flexibility for steadyoperation at least 135° C. This test is known as the heat shock test.

The final thermal requirement of a magnet wire which is to be used atelevated temperatures is that the dielectric strength of the enamel filmremains sufficiently high at elevated temperatures after a long periodof operation so that no short circuits occur between adjacent magnetwires. We have found that for a magnet wire to be satisfactory foroperation at a temperature of at least 135° C. its dielectric strengthshould not be less than two-thirds of the initial dielectric strengthafter being maintained at a temperature of 175° C. for 100 hours in anoven circulating air having a relative humidity of 25 percent at roomtemperature. This change in dielectric strength is measured as thedielectric strength, volts (or volts per mil) twisted pairs, both beforeand after the 175° C. heat aging.

Objects Of The Invention

It is the principal object of the present invention to produce a coatingcomposition which is highly aqueous in solvent composition, is low incost, may be utilized in existing commercial coating equipment, andwhich produces coatings suitable for severe, heavy duty application,particularly electrical uses such as wire enamels and the like.

More specifically, it is the objective of the present invention toprovide a resin system finding particular but not exclusive utility inmagnet wire enamel formulations, which is commercially competitive withexisting magnet wire compositions, which is highly aqueous therebyeliminating organic solvent disposal, toxicity and combustion problems,and which reduces or eliminates pollution problems, and is thus anecologically and environmentally positive system.

Another object of the present invention is to enable the utilization ofwater soluble polyester resins for applications such as electricalinsulation and magnet wire application, and more particularly to upgradeaqueous polyester resin containing systems to produce electrical gradecoatings which are thermally stable and which have improved mechanicaland chemical properties.

A further object of the present invention is to provide a stable,economical, highly water soluble resin system suitable for use in a widevariety of coating applications including electrical coatingapplications such as magnet wire enamels.

Still a further object is to provide a water soluble resin system forcoating applications, which resin system produces coatings which oncuring, are clear, tough, flexible, dielectric and heat stable.

Another object is to provide a water based coating medium of theforegoing character, which is suitable for use in existing conventionalcoating equipment, including conventional wire towers for coatingcontinuous filament materials such as magnet wire.

A more detailed object of the present invention is to provide an aqueousbased coating medium of the foregoing characteristics from which a resincoating can be applied to a substrate and which when so applied isreadily cured to a tack-free state, evidences a minimum weight loss oncure, and does not darken, lose its flexibility or depolymerize onaging.

SUMMARY OF THE INVENTION

In accordance with the foregoing objects, the present inventioncontemplates a coating composition having a substantially aqueous baseand embodying in admixture, a water soluble polyester coating resin anda low molecular weight orthoamic acid diamine produced as the reactionproduct of an aromatic diamine and an aromatic dianhydride in the molarratio of m/(m-1) respectively where m has a value of from 2 to about 7.The polyester and orthoamic acid diamine are admixed in the ratio offrom 1 to 10 parts polyester and from 1 to 10 parts orthoamic aciddiamine. Additional ingredients may be added including accelerators aswell as minor amounts of water soluble resins such asphenol-formaldehyde resins, aminoplasts, epoxy resins and the like.

The polyester resins are conventional commercially available watersoluble polyester resins conventionally used in coating operations,while the orthoamic acid diamine is produced as the reaction product ofan aromatic diamine and an aromatic dianhydride. In the latter process,the diamine is first dissolved in an appropriate solvent and thedianhydride is then slowly added to form an orthoamic acid diaminereaction product in the solvent system. Where the molar ratio ofaromatic diamine to aromatic dianhydride is two-to-one, the reactionproduct is a diamide diacid diamine. To provide an aqueous base diaminesystem, the reaction product, in the water-miscible organic solventsystem, is reacted with a volatile base such as ammonia or primary orsecondary amine, to produce a water soluble compound. Water is thenadded to provide an essentially aqueous based solution which may bemixed with an aqueous solution of a polyester resin.

Upon application of a coating of the solution to a substrate, such asmagnet wire, the coating may be cured at a temperature between 100° and500° C. to drive off the water and solvent and copolymerize thepolyester and orthoamic acid diamine. The result is a clear, flexible,tough, adherent, solvent resistant dielectric thermally stable polymeiccoating. Unexpectedly, the coating film thus produced exhibits theforegoing properties even when the polyester resin constitutes the majorportion of the solids. The resultant coatings exhibit propertiescomparable to coatings achieved from conventional magnet wire polyesterresins applied from organic systems. The aqueous based coating medium ofthe present invention is stable and neither gells nor coagulates norforms a precipitate on standing, and has the advantages attributable toan aqueous base system as contrasted to an organic solvent based systeminsofar as the environment, ecological and pollution factors areconcerned. The surprising result is that coatings produced from aqueouspolyester resin containing media are upgraded with respect to physicalproperties comparable to like properties achieved from presentcommercial coating materials.

Description of the Preferred Embodiment

The coating composition of the present invention is formed by theadmixture, in water or a highly aqueous solvent, of a water solublepolyester or polyestermide resin with an aromatic orthoamic aciddiamine, particularly an aromatic diamide diacid diamine. Additionalwater soluble resin materials, such as phenolformaldehyde resins, epoxyresins, and aminoplasts, may be added to the mixture. The water solublepolyesters, polyesterimides, phenol-formaldehyde resins, epoxy resinsand aminoplasts are all widely known materials which are readilyavailable in the commercial market. The aromatic orthoamic acid diamine,such as the aromatic diamide-diacid-diamine, is an oligomeric materialproduced by reacting an aromatic diamine and an aromatic dianhydride inthe molar ratio from two-to-one, respectively, to about seven-to-six,respectively, with the former generally in the amount of one molegreater than the latter. Such compounds, containing a one mole excess ofthe diamine, are low molecular weight, essentially monomeric compoundsas distinguished from high molecular weight polymeric compounds, and maybe generally expressed by the formula X(YX)_(n) YX where X represents anaromatic diamine, Y represents an aromatic dianhydride, and n has avalue of from 0 to 5. Defined another way, the orthoamic acid diaminesreferred to are the reaction product of m-moles of an aromatic diamineand (m-1) moles of an aromatic dianhydride where m has a value of from 2to about 7, and a preferred value of from 2 to 5. Aromaticdiamide-diacid-diamines and the manner of making and using them ascoating materials to produce coatings and coated substrates aredescribed in detail in copending application Ser. No. 475,483, filedJune 3, 1974, by Marvin A. Peterson, for Coating Composition and Methodof Coating Substrates Therewith, and assigned to the same assignee asthe present invention. The higher molecular weight aromatic orthoamicacid diamines produced by reacting the diamine and dianhydride in molarratios defined above are nevertheless generally characterized as "lowmolecular weight" monomeric materials and are produced in substantiallythe same manner as described in application Ser. monomerics 475,483.These monomerics should be distinguished from the polymeric highmolecular weight polyorthoamic acids disclosed in U.S. Pat. No.3,652,500, issued Mar. 28, 1972, to M. A. Peterson for "Process forProducing Polyamide Coating Materials by Endcapping" and U.S. Pat. No.3,663,510, issued May 16, 1972, to M. A. Peterson for "Process forProducing Polyamide Coating Materials."

All of the above materials are mutually soluble in water or highlyaqueous solvents, and are compatible with each other in solution. As themolecular weight of the orthoamic acid diamine increases (n>20),however, the compatibility of the diamine with the other water solublepolymers decreases rapidly, to the end that water soluble polyorthoamicacid polymers, as described in U.S. Pat. No. 3,652,500 and U.S. Pat. No.3,663,510 are incompatible with other water soluble polymers such aspolyesters. Accordingly, it has heretofore proven impossible to preparea stable, homogeneous coating medium which incorporates both watersoluble polyester or polyesterimide resins and water solublepolyorthoamic acid resins.

Polyester Resin

A wide variety of water soluble polyester resins find application inconnection with the present invention. It has been ascertained that thebase polymers which present the requisite thermal stability for use inconnection with the present invention are of the polyester genus, andare generally formed from aromatic anhydrides and acids, such astrimellitic anhydride and acid and phthalic anhydrides and acids.Extensive developments have been made in the field of water solublepolyesters for coatings, and many such materials are in widespread usein the form of pigmented, but otherwise quite clear, highly aqueoussolvent systems. While such polyester resins are readily available ascommercial products, their exact formulation is most often a proprietarymatter with the particular manufacturer. It is possible, however, asdemonstrated in the following examples, to formulate and prepare a widevariety of such polyester resins from known materials by following knownprocedures.

The polyester resins are condensation products of a polycarboxylic acidand a polyhydric alcohol. To achieve the desired thermal stability, thepreferred polycarboxylic acid is an aromatic acid or anhydride. Thecondensation product desirably has an acid number of at least 45, andgenerally between about 45 and 80. Among the useful polyester resins arethe polyesters produced as the reaction product of such aromaticanhydrides and acids as trimellitic anhydride, phthalic acid, phthalicanhydride, terephthalic acid, isophthalic acid, and certain diacidreaction products such as the reaction product of 2 moles of trimelliticanhydride and 1 mole of 4,4'-methylene dianiline, thus: ##STR1##together with such aliphatic diacids as adipic acid; and such polyhydricalcohols as propylene glycol. neopentyl glycol, butylene glycol,diethylene glycol, trishydroxyethylisocyanurate, and the like.

Polyester resins and aqueous solutions thereof useful in this inventionare selected from a wide variety of polyester resins which generallyproduce coating films having good impact resistance and hardness, areflexible and adherent to substrates to which they are applied and can beapplied from both organic and aqueous solvent systems. Such polyesterswill have an acid number in excess of 45 and generally between 45 and 80and possibly higher. Below 45 gellation may result. The polyesters arehighly stable and maintain their clarity and color over a long period oftime.

In the selection of polyester resins for application to magnet wire fromaqueous solutions, the use of such materials in commercial wire towersmust be considered. Coating resins utilized in such towers must becurable at the wire speed, usually between 40 and 60 feet per minute,and particularly at wire speeds of 50-55 feet per minute, and at thetemperatures prevailing in the tower. Among other factors, polyesterresins to be applied from aqueous solutions will desirably have ahydroxyl value in the range of from about 100 to about 200 andpreferably between about 110 and about 160. Also, such polyester resins,in consideration of electrical applications, will have an aromatic toaliphatic ratio of 22 to 40 molar percent. In admixture with theorthoamic acid diamines hereinafter described, the aqueous coatingsolutions will desirably have an aromatic to aliphatic molar ratio offrom about 25 to about 50 percent. The above criteria can be utilized toselect appropriate reactants for producing the polyester resins as wellas the admixture of the polyester resins with the orthoamic aciddiamines. In this manner coating solutions suitable for application byselected procedures, such as commercial wire towers can be readilyformulated.

Appropriate accelerators or catalysts may be added to the polyesterresin system. Appropriate catalysts for the polyester resins are certainorganometallic compounds such as the titanium chelates. These titaniumchelates are commerciall available from E. I. duPont de Nemours and Co.as Tyzor OG tetraoctylene glycol titinate, Tyzor TE triethanolaminetitinate, and Tyzor LA ammonium salt of titanium lactate, as well asfrom other commercial sources. As shown in the examples, theaccelerators or catalysts improve the cure of the coating compositionscontaining polyester resins and the orthoamic acid diamines withoutadversely affecting the properties of the cured films.

The number and variety of water reducible or soluble polyester resinswith the above characteristics and properties is substantiallyunlimited. While examples are presented showing the preparation and useof a variety of polyester resins, it is not intended to either limitthis disclosure or to show how many kinds of polyesters can be prepared.It is rather intended to demonstrate that the present invention involvesthe surprising and unexpected discovery that, by the admixture of awater soluble polyester resin and a water soluble orthoamic aciddiamine, electrical grade, thermally stable coatings may be produced.

Water soluble polyester resins by themselves, generally speaking, do nothave the requisite properties for application from aqueous solutions toform electrical grade coatings, particularly wire enamels. Efforts havebeen made to upgrade water reducible polyester resins by the additionthereto of such known electrical grade water reducible resins as thepolyamide acids. These two resins, though both water soluble, have beenfound to be incompatible, and in admixture result in or separate intoboth a polyester rich layer and a polyamide acid rich layer.

While other resins, such as phenol-formaldehyde resins, epoxy resins,and the like may be blended in water soluble form, with water solublepolyester resins, the results are less than satisfactory as far aselectrical properties ae concerned, although many of the properties ofcoatings produced from the combined polymers show improvement over theproperties achieved from coatings of the individual polymers.

Orthoamic acid diamines

In accordance with the present invention, it has been discovered thatcertain low molecular weight oligomeric aromatic orthoamic aciddiamines, and particularly aromatic diamide-diaciddiamines, are not onlyfully compatible with aqueous polyester resin solutions, but thatcoatings produced from such an admixture are clear, tough, flexible andthermally stable, and possess surprisingly good electrical properties,including properties which lend the resin solution to use as a magnetwire enamel in conventional wire coating equipment. The orthoamic aciddiamines referred to are low molecular weight compounds, and aredistinguished thereby from the known polyorthoamic acid polymersdescribed in U.S. Pat. No. 3,179,614, issued Apr. 20, 1965, to W. M.Edwards for "Polyamide-acids, Compositions Thereof, and Process forTheir Preparation," and U.S. Pat. No. 3,652,500 and U.S. Pat. No.3,663,510 referred to above. The coating material described in U.S. Pat.No. 3,652,500, after endcapping with a diamine, is a long chain, highmolecular weight, polyamide acid diamine. Even in the water solublestate, however, such high molecular weight material is incompatible withwater solutions of water soluble polyester resins.

As used herein, the term "orthoamic acid diamine" or, alternatively, theterm "oligorthoamic acid diamine" is intended to refer to and define lowmolecular weight compounds produced by the reaction of m-moles of anaromatic diamine with (m-1)-moles of an aromatic dianhydride, where mhas a value of between 2 and about 7. Because the orthoamic aciddiamines are of relatively low molecular weight and have few repeating"mer" groups, they may for convenience be referred to as "oligomers" asdistinguished from "polymers" which conventionally are of high molecularweight with many repeating groups. In this respect, these low molecularweight compounds are clearly distinguishable from the high molecularweight polymers, amine endcapped polyamic acid diamines, disclosed inU.S. Pat. No. 3,652,500, for which the value of m would be in excess of20. Expressed another way, the orthoamic acid diamines referred toherein have the general formula X(YX)_(n) (YX) where X represents anaromatic diamine, and Y represents an aromatic dianhydride, and n has avalue of from 0 to about 5. The preferred range of values of m is 2 to4, or the equivalent preferred range of values of n is 0 to 2. Where mis 2 or n is 0, the aromatic orthoamic acid diamine is an aromaticdiamide-diacid-diamine. The aromatic diamide-diaciddiamines aredescribed in detail in copending application Ser. No. 475,483, filedJune 3, 1974, for "Coating Composition and Method of Coating SubstratesTherewith." These compounds are oligomeric materials which are renderedwater soluble by the use of ammonia or a volatile amine. Thesediamide-diacid-diamines may be applied as coatings on a substrate fromeither an organic or an aqueous solution as a coating medium to form ahighly cross-linked polymeric coating on a substrate.

The orthoamic acid diamines useful in this invention are those lowmolecular weight aromatic compounds produced as the reaction product ofan aromatic diamine and an aromatic dianhydride, with the diamine in aone mole excess, as defined above. The initial reaction takes place inan aprotic solvent system which is nonreactive with or inert to thediamine and dianhydride reactants. The reaction is carried out at atemperature below about 70° C. so that there is a negligible level ofimidization, resulting in the orthoamic acid product, which may becharacterized, where the reactants are to a two-to-one ratio, as adiamide-diacid-diamine. If the reaction solution is heated undercontrolled conditions, certain desired levels of imidization can beachieved. However, if the heating is carried too far, such as to producean imide level greater than about 90%, depending upon the particulardiamine and dianhydride selected, the imide thus formed precipitates asan insoluble, inflexible, unreactive solid precipitant. Following theformation of the reaction product of the orthoamic acid diamine, such asthe diamide diacid diamine, in an organic solvent system, a volatilebase is added in an amount sufficient to react with that reactionproduct to produce a water soluble compound. The system is then dilutedwith water to provide an esentially aqueous solution.

The initial reaction between the diamine and the dianhydride is carriedout in a high solids content organic solvent system, with the reactantsin the desired molar ratio, such as the ratio of two-to-one,respectively, that is in the molar ratio of two moles of aromaticdiamine to one mole of aromatic dianhydride. To illustrate, a diamine,in the proportion of two moles, is first dissolved in an organicsolvent. A dianhydride, in proportion of one mole, is then slowly addedor trickled into the diamine solution. The temperature is maintainedgenerally at about 70° C. or below, and preferably at about 50° C. orbelow. As the dianhydride is trickled into the diamine solution, onemole of the dianhydride immediately reacts with two moles of the diamineto produce the diamide diacid diamine monomeric coating materialdesired. It has been observed that, if the one mole of dianhydride isdissolved first, and the two moles of diamine is next charged,polymerization occurs resulting in a higher molecular weight polymericmaterial and an excess of diamine. On the other hand, if dry dianhydrideis added rapidly, such as in a chunk or as a slug, the dianhydridereacts faster than it dissolves, thereby leaving "islands" of unreacteddianhydride surrounded by reacted dianhydride.

In order to convert the aromatic orthoamic acid diamine, such as thearomatic diamide diacid diamine reaction product, that is the oligomeror "polymer precursor," to an aqueous based system, a volatile base isadded in an amount sufficient to conver the reaction product to a watersoluble form, followed by dilution of the system with water to form anaqueous-organic coating medium, without hydrolyzing or destroying thediamide diacid diamine monomer. This reaction is generally initiallycarried out in the organic solvent at a solids level greater than 40%solids by weights, and more often greater than 50% solids by weight.

The aromatic dianhydrides that are useful in accordance with thisinvention are those having the general formula: ##STR2##wherein R is atetravalent radical containing two benzene rings joined by a chemicallyinert, thermally stable moiety selected from the group consisting of analkylene chain having from 1 to 3 carbon atoms, an alkyl ester, asulfone and oxygen, each pair of carboxyl groups being attached todifferent adjacent carbon atoms of a single separate ring. Thesedianhydrides include, for example, 4,4'-(2-acetoxy-1,3-glyceryl)bis-anhydro trimellitate,

3,3',4,4'-benzophenonetetracarboxylic dianhydride,

bis(3,4-dicarboxyphenyl) sulfone dianhydride,

bis(2,3-dicarboxyphenyl) methane dianhydride,

2,2-bis (3,4-dicarboxyphenyl) propane dianhydride,

bis(3,4-dicarboxyphenyl) ether dianhydride,

2,2-bis(2,3-dicarboxyphenyl) propane dianhydride,

1,1-bis(2,3-dicarboxyphenyl) ethane dianhydride,

1,1-bis(3,4-dicarboxyphenyl) ethane dianhydride, and the like.

The aromatic diamines that are useful in accordance with this inventionare those having the general formula:

    H.sub.2 N-R'-NH.sub.2

wherein R' is a divalent radical selected from the group consisting of##STR3## wherein R'" is an aryl and R"" is an alkyl or an aryl grouphaving 1 to 6 carbon atoms, n is an integer of from 1 to 4 and m has avalue of 0, 1 or more and ##STR4## wherein R" is selected from the groupconsisting of an alkylene chain having 1-3 carbon atoms, ##STR5##wherein R'" and R"" are as above-defined and x is an integer of at least0. In general, the diamines contain between 6 and 16 carbon atoms, inthe form of one or two six-membered rings. Such diamines may also betermed or referred to as di-primary amines.

Specific diamines which are suitable for use in the present inventionare:

m-phenylene diamine,

p-phenylene diamine,

4,4'-diaminodiphenyl propane,

4,4'-diaminodiphenyl methane, benzidine,

4,4'-diaminodiphenyl sulfide,

4,4'-diaminodiphenyl sulfone,

3,3'-diaminodiphenyl sulfone,

4,4'-diaminodiphenyl ether,

2,6-diaminopyridine,

bis-(4-aminophenyl) diethyl silane,

bis-(4-aminophenyl) phosphine oxide,

bis-(4-aminophenyl) -N-methylamine,

1,5-diamino naphthalene,

3,3'-dimethyl-4,4'-diamino-biphenyl,

3,3'-dimethoxy benzidine,

m-xylylene diamine,

p-xylylene diamine,

1,3-bis-gamma-aminopropyltetraphenyl disiloxane, and mixtures thereof.

The organic solvents utilized in accordance with this invention arethose organic solvents having functional groups which do not react witheither of the reactants, the aromatic diamines or the aromaticdianhydrides, to any appreciable extent. In addition to being inert withrespect to the reactants, the solvent utilized must be inert to and asolvent for the reaction product. In general, the organic solvent is anorganic liquid, other than either reactant or homologs of the reactants,which is a solvent for at least one of the reactants, and which containsfunctional groups other than monofunctional, primary and secondary aminogroups and other than the monofunctional dicarboxyl anhydro groups. Suchsolvents include, for example, N-methyl-2-pyrrolidone (sometimesabbreviated NMP), dimethylsulfoxide (DMSO), N-formyl moropholine (NFM),or such organic solvents as N,N-dimethylmethoxy-acetamide,N-methyl-caprolactam, tetramethylene urea, pyridine, dimethylsulfone,hexamethylphosphoramide, tetramethylenesulfone, formamide,N-methylformamide, N,N-dimethyl formamide, butyrolactone, orN-acetyl-2-pyrrolidone. The solvents can be utilized alone, as mixtures,or in combination with relatively poorer solvents such as benzene,toluene, xylene, dioxane, cyclohexane, or benzonitrile.

The volatile bases that are useful in connection with the presentinvention for producing a water soluble monomeric reaction product,include ammonia (NH₃), ammonium hydroxide (NH₄ OH), ammonium carbonate[(NH₄)₂ CO₃ ] and primary and secondary aliphatic amines containing upto four carbon atoms, such as methylamine, ethylamine, secondarybutylamine, isopropylamine, dimethylamine, diethylamine, dibutylamine,and the like.

In the initial reaction for preparing a coating composition embodyingthe present invention, utilizing an aromatic diamide diacid diamine, anaromatic diamine is reacted with an aromatic dianhydride in the molarratio of two-to-one respectively, or in other words in the ratio of twomoles of the former to one mole of the latter. With reference to theabove formula X(YX)_(n) (YX), the aromatic diamide diacid diamine isproduced when n equals zero, and the molar ratio m/(m-1) holds true whenm equals two. The reaction product may be expressed by the generalformula: ##STR6## wherein the arrows denote isomerisim, that is wheregroups may exist in interchanged positions, and R and R' are as definedabove. Such an oligomeric reaction product or a "polymer precursor" maybe generally characterized as a "diamide-diacid-diamine." Uponadditional of a volatile base, a compound having the following generalformula results: ##STR7## wherein X indicates the positive ion of thevolatile base, and R and R' are as defined above. Such compound is watersoluble so that the coating composition can be diluted with water toform an aqueous-organic coating medium.

To illustrate the preparation of the diamide-diaciddiamine morespecifically, the aromatic diamine, 4,4'-diaminodiphenyl methane, alsotermed p,p-methylene dianiline (abbreviated MDA or simple M), was mixedwith an aromatic dianhydride, 3,3', -4,4'-benzophenonetetracarboxylicdianhydride (abbreviated "BPDA" or simply B), in the molar ratio of twomoles of diamine to one mole of dianhydride, in an anhydrousN-methyl-2-pyrrolidone (NMP) solvent at about 50% solids. The reactionwas spontaneous at a temperature below 70° C. The resulting product isthe oligomer or "polymer precursor" having the formula ##STR8## whichformula may be conveniently abbreviated as "MBM." For more details onthe reaction of the diamine and dianhydride see U.S. Pat. Nos. 3,652,500and 3,663,510 referred to above.

Similarly, p,p'-methylene dianiline was condensed with4,4'-(2-acetoxy-1,3-glyceryl)bis-anhydro trimellitate, in the molarratio of two-to-one, respectively in NMP solvent, at greater than 40%solids and at a temperature generally below 70° C. The resultingoligomer or "polymer precursor" produced has the formula ##STR9## whichmonomeric compound may be abbreviated as "MAM."

Both the MBM and the MAM oligomeric compounds are insoluble in water,but are made water soluble by the addition of a volatile base such asammonia or a volatile amine. The result is a water solublediamide-diaciddiamine oligomer or polymer precursor, which is thencombined in admixture with a water soluble polyester resin describedabove and sufficient water to produce a coating medium having thedesired solids content. In a selected application, depending on thepolyester selected, coatings produced from the medium thus produced arecurable in a predetermined temperature range, usually between 150° C.and 250° C., to produce clear, non-tacky films with excellent adhesionto the substrate.

Oligomeric or "polymer precursor" compounds have been prepared fromvarious combinations of aromatic dianhydrides and aromatic diamines.Among such compounds are those prepared with the following molar ratio:2.0 moles 1,3-diamino benzene, also termed m-phenylene diamine, and 1.0mole 3,3',4,4' benzophenonetetracarboxylic dianhydride; 2.0 moles4,4'-diaminodiphenyl ether, also termed p,p'-oxydianiline, and 1.0 moleof 3,3',4,4'-benzophenone-tetracarboxylic dianhydride; 2.0 molesm-phenylene diamine and 1.0 mole 4,4'-(2-acetoxy-1,3-glyceryl)bis-anhydro trimellitate; 2,0 moles p,p'-oxydianiline and 1.0 mole4,4'-(2-acetoxy-1,3-glyceryl)bis-anhydro trimellitate. Such compoundswere prepared in an N-methyl-2-pyrrolidone (NMP) solvent, ammonia or asuitable amine was added, and the solutions diluted with water to a 25%solids by weight solution.

Admixtures of aqueous solutions of polyester resins and aqueoussolutions of diamide-diacid-diamines prepared as above-described areprepared by mixing appropriate amounts of each solution to produce thedesired ratio of components. Additional water may be added if necessaryto produce a coating medium of the desired consistency for theparticular coating operation.

While the weight ratio of polyester resin to orthoamic acid diamine,such as the diamide-diacid-diamine, can vary widely, that is from about9 parts polyester and 1 part orthoamic acid diamine to about 1 partpolyester and 9 parts orthoamic acid diamine, the use of relativelysmall amounts of the orthoamic acid diamine has produced highlysatisfactory results. It is believed that even a small amount of theorthoamic acid diamine produces extensive cross-linking in thepolyester, leading to coatings having the desired electrical properties.

Upon the heat curing of the admixture of polyester and orthoamic aciddiamine it is believed that a highly cross-linked ester-amide-imidestructure is formed, resulting in the unique properties achieved. Thehighly cross-linked structure with the imide linkages is apparentlysufficient to enhance the properties of the polymer coating and promotethe resulting cured film to an electrical grade material. Surprisingly,even relatively small amounts of the orthoamic acid diamine aresufficient to increase and improve the properties of the coating filmover and above properties of films achieved from the polyester resinalone. Moreover, in contrast to attempts to blend aqueous solutions ofpolyesters with aqueous solutions of polyorthoamic acids, which resultin separate phases, the orthoamic acid diamine and polyester blends ofthe present invention are fully compatible and produce a homogeneousaqueous solution.

Both the polyester and the orthoamic acid diamine are made water solubleby the addition of a volatile base such as ammonia, ammonium carbonateand primary and secondary aliphatic amines. The volatile base may beadded either before or after admixing the polyester and orthoamic aciddiamine. In other words, an organic polyester solution may be admixedwith the organic orthoamic acid diamine solution and then the mixturemade water soluble by the addition of a volatile base. Alternatively,the volatile base may be added to each component separately, eachcomponent being diluted thereafter with water and the aqueous solutionsmixed. In either case, the components are completely compatible witheach other. Coatings can then be applied from the combined aqueoussolution to whatever substrate may be selected, including copper oraluminum, as well as magnet wire, and the coating cured to produce thedesired cured film.

The coating mixture of the polyester and the orthoamic acid diamine maybe prepared in yet another way. After preparing the polyester resin andwhile it is still in the reaction vessel it is diluted with a solventwhich is also a solvent for the orthoamic acid diamine. The aromaticdiamine reactant as described above is then added to the polyestersolution. A solution of the aromatic dianhydride reactant is then addedto the polyester and diamine solution and the reaction proceeds in situ.Reactivity of the anhydride is such that it reacts preferentially withthe diamine to form the orthoamic acid diamine directly in the polyestersolution. Thereafter a volatile base may be added and the solutiondiluted with water to form the desired aqueous spaced coating medium.The disadvantage of the in situ procedure however insofar as subsequentelectrical properties are concerned, is that any reaction of thedianhydride with hydroxyl groups of the polyester leaves residualcarboxyl groups in the polymer and in the subsequently cured coating,which may adversely affect electrical properties of the coating. Also,with the in situ preparation it may be difficult to accurately controlthe formation of the desired orthoamic acid diamine.

It should be further noted that the cured film may be overcoated with aNylon coating as is conventional practice in the magnet wire industry.It has been observed that the polyesterorthoamic acid diamine curedcoating provides a surface which is fully receptive and adherent to theNylon overcoating.

Polymeric Additives

There may be additionally admixed with the polyester resin minor amountsof a variety of water soluble polymers. Among the illustrative polymers,are water soluble phenolformaldehyde resins, water soluble aminoplastsand water soluble epoxy resins, as well as numerous other materialswhich are conventionally added to modify the properties of coatingmaterials. A wide variety of the above water soluble resins and othermaterials are well known and commercially available from a number ofsources. For example, water soluble phenol-formaldehyde resins aredescribed in the Kirk-othmer "Encyclopedia of Chemical Technology," Vol.15, Pages 176-208, 2nd Ed., John Weley and Sons, Inc., 1968, and arecommercially available from Union Carbide Corporation. Union Carbideresin BRLA-2854, an amine catalyzed resin, has been added to thepolyester -orthoamic acid diamine solution described above in the amountof between about 2% and about 5% by weight. A commercial grade ofhexamethoxymethylmelamine, "Aminoplast" resin, such as American CyanamidCompany resin Cymel 301, a water soluble hexamethoxymethylmelamineresin, can be added, and the examples herein illustrate the addition ofsuch a resin to the solution in the amount of between about 2 and about5% by weight. Such resins are compatible with polyester resins, epoxyresins and many others. See Gams, Widmer and Fisch, Helv. Chem. Acta. 24302-19E (1941). A water soluble epoxy resin, such as Ciba-GeigyCorporation resin Araldite DP-630 can be utilized to advantage. Theexamples herein illustrate the use of a water soluble epoxy resin in thepolyesterorthoamic acid diamine solution in the amount of between about2 and about 5% by weight. The addition of the various additives in minoramounts produces homogeneous solutions and the resins are all fullycompatible, in the proportions utilized, with the polyester-orthoamicacid diamine solution.

Flow Control Agents

In order to control the flow characteristics of the coating solution, avariety of surfactants, flow control agents and the like may be added tothe aqueous polyester orthoamic acid diamine coating solution. Among thewide variety of available flow control agents are the well knownsurfactants, including fluorocarbon surfactants, carboxypropylterminated dimethylsiloxane polymer flow agents,nonylphenoxypoly(ethyleneoxy)ethanol, also referred to asnonylphenolethylene oxide adduct, and a mixture off cresylic acid-phenolblend with n-butyl alcohol. The surfactants are generally added in theamount of approximately 100 parts per million although the cresylicacid-phenol blend and n-butyl alcohol will generally be added in amountssubstantially greater and up to about 6% by weight of the coatingmedium.

EXAMPLES

In the following examples, Examples 1 through 13 inclusive describe thepreparation of illustrative water solutions of various orthoamic aciddiamines useful in this invention; Examples 14 through 22 describe thepreparation of illustrative water solutions of polyester resins usefulin this invention; Example 23 describes the preparation of a watersolution of a high molecular weight polyorthoamic acid diamine followingthe teachings of the prior art; Examples 24 through 34 demonstrate thegeneral incompatibility of aqueous solutions of a high molecular weightpolyorthoamic acid diamine, as prepared according to Example 23, withwater solutions of polyesters, such as those prepared according toExamples 14 through 22; and Examples 35 through 75 illustrate thepresent invention.

EXAMPLE 1

To a reactor equipped with a stirrer, a nitrogen atmosphere, an entryport, and a thermometer well, was charged 132.2 g.N-methyl-2-pyrrolidone having a water content below 200 p.p.m. Thesolvent was agitated and 132.2 g. (0.667 mole) 4,4'-diaminodiphenylmethane (99% purity) was added over a period of about 30 sec. Thereresulted a clear solution I. To a second, similar reactor, equipped witha heating mantle, was charged 160.7 g. N-methyl-2-pyrrolidone having awater content below 200 p.p.m. The solvent was agitated and heated to atemperature of 60° C., whereupon with agitation 160.7 g. (0.333 mole)4,4'-(2-acetoxy-1,3-glyceryl)bisanhydrotrimellitate (99% purity) wasadded over a period of about 3 min. The temperature rose to about 80° C.Stirring was continued for another 5 min., resulting in a clearhomogenous solution II. The solution II was cooled to about 43° C. andallowed to trickle into solution I over a period of about 2 min. withagitation. The temperature rose to a maximum of 75° C. during the next 5min. period of agitation. There resulted a clear solution III. Thepercent imidization was found to be 0.7 as determined by titration forthe carboxylic acid content in pyridine with tetrabutylammoniumhydroxide and with thymol blue as the indicator. The viscosity was 200cps. at a solids level of 50.0% as the orthoamic acid. Upon exposing0.50 g. of sample in an aluminum cup having a diameter of about 55 cm.to a temperature of 150° C. for a period of 90 min., the solids levelwas measured as 47.9%.

The idealized formula of the resin thus produced in solution is:##STR10##

To 585.0 g. of the solution III, there was injected, subsurfacewise andwith agitation, 75.0 g. of a 40% aqueous solution of dimethylamine, overa period of 2 min. The resulting solution IV was clear and dilutablewith water. With agitation continuing, a mixture of 17.0 g. ethyleneglycol n-butyl ether, 5.8 g. N-methyl-2-pyrrolidone, 88.0 g. water, 35.2g. n-butyl alcohol, and sufficient nonylphenolethylene oxide adduct toresult ultimately in 45 p.p.m., was added resulting in a clear solutionV having a solids level at 37.5% as the orthoamic acid in solution, and36.0% as a cured film. The solution V had a viscosity of 185 cps., and asurface tension of 38.7 dynes/cm.

EXAMPLE 2

To another 585 g. of solution III of Example 1, there was injected,subsurfacewise and with agitation 44.7 ml. of 28% ammonia water over aperiod of 2 min. The resulting solution IV was clear and dilutable withwater. With agitation continuing, a mixture of 17.0 g. ethylene glycoln-butyl ether, 5.8 g. N-methyl-2-pyrrolidone, 104.0 g. water, 35.2 g.n-butyl alcohol and sufficient nonylphenolethylene oxide adduct toresult ultimately in 45 p.p.m., was added resulting in a clear solutionV, having a solids level at 37.6% as the orthoamic acid in solution and36.0% as a cured film. The solution had a viscosity of 224 cps., surfacetension of 39.4 dynes/cm., and a pH of 7.6 at 24° C.

EXAMPLE 3

To the first of the reactors of the type referred to in Example 1 wascharged 132.2 g. N-methyl-2pyrrolidone having a water content below 200p.p.m. The solvent was agitated and 132.2 g. (0.667 mole) of4,4'-diaminodiphenyl methane (99% purity) was charged with agitationover a period of 30 sec., resulting in a clear solution I. To the secondreactor was charged 429.4 g. N-methyl-2-pyrrolidone having a watercontent below 200 p.p.m. The solvent was agitated and heated to atemperature of 50° C. whereupon 107.3 g. (0.333 mole) of3,3',4,4'-benzophenonetetracarboxylic dianhydride was charged over aperiod of 2 min. with agitation. Stirring was continued for another 5min. and the solution II allowed to cool to 30° C. The solution II ofdianhydride was then trickled into solution I with agitation over aperiod of 3 min. The stirring was continued for a period of 10 min.resulting in a maximum temperature of 55° C. There resulted a clearsolution III. The material was titrated for carboxylic acid and thepercent imidization found to be less than 1%. Viscosity was 104 cps. at24° C. at a solids level of 29.9% as the orthoamic acid solution and28.4% as a cured film, the latter being determined by exposing one gramof sample in an aluminum cup having a diameter of about 5.5 cm. to atemperature of 150° C. for a period of 90 min.

The idealized formula of the resin thus produced in solution is##STR11##

For each 400.0 g. of solution III was added 22.4 ml. 28% aqueousammoniacal solution, subsurfacewise and with agitation, over a period of1.5 min. The resulting solution IV was clear and dilutable with water.To the reactor was then charged 21.1 g. of a mixture of 95% n-butylalcohol and 5% N-methyl-2-pyrrolidone and sufficient amount ofnonylphenolethylene oxide adduct such that the resulting total systemhad about 60 p.p.m. of the latter component. There resulted a clearsolution V having a viscosity of 112 cps at 24° C. at a 27.0% solidslevel as the orthoamic acid and 25.6% as a cured film. The latter wasdetermined by exposing a thin film of the liquid to 150° C. for a periodof 90 min. This solution V was water reducible or dilutable.

EXAMPLE 4

To a reactor equipped with a stirrer, nitrogen atmosphere, entry port,and a thermometer well, was charged 108.1 g. N-formyl morpholine havinga water content below 200 p.p.m. The solvent was agitated and 108.1 g.(1.000 mole) m-phenylene diamine was charged over a period of about 30sec. There resulted a clear solution I. To a second, similar reactorequipped with a heating mantle, was charged 161.0 g. N-formyl morpholinehaving a water content below 200 p.p.m. The solvent was agitated andheated to a temperature of 50° C. whereupon, with agitation, 161.0 g.(0.500 mole) 3,3',4,4'benzophenonetetracarboxylic dianhydride wascharged over a period of 3 min. There resulted a temperature rise to 76°C. Stirring was continued for another 5 min. resulting in a clearhomogeneous solution II. The solution II was cooled to about 40° C. andallowed to trickle into solution I over a period of about 2 min. withagitation. The temperature rose to a maximum of 73° C. during the next 5min. period of agitation. The resulting clear solution III had aviscosity of 290 cps. and a solids level of 50.0% as the orthoamic acid.

To 269. 1 g of solution III was injected subsurfacewise and withagitation, a mixture of 100 ml. water and 33.7 ml. of 28% ammonia waterover a period of 2 min. The resulting solution IV was clear anddilutable with water. With agitation continued, a mixture of 23.4 g.n-butyl alcohol, 2.2 g. N-formyl morpholine, 100 ml. water andsufficient nonylphenolethylene oxide adduct to provide 60 p.p.m. in thetotal formulation, was added, resulting in a clear solution V having asolids level of 25.9% as the orthoamic acid and 24.2% as a cured film.The solution had a viscosity of 288 cps., a surface tension of 37.0dynes/cm., and a pH of 7.4 at 24° C.

EXAMPLE 5

To a reactor equipped with a stirrer, nitrogen atmosphere, entry portand a thermometer well, was charged 200.4 g. N-methyl-2-pyrrolidone. Thesolvent was agitated, and 200.4 g. (1.000 mole) 4,4'-diaminodiphenylether was charged over a period of 30 sec. There resulted a clearsolution I. To a second, similar reactor equipped with a heating mantle,was charged 161.0 g. M,N-dimethylformamide. The solvent was heated to atemperature of 50° C., whereupon, with agitation, 161.0 g. (0.500 mole)3,3',4,4'-benzophenonetetracarboxylic dianhydride was charged over aperiod of about 3 min. There resulted a temperature rise to about 70° C.Stirring was continued for another 5 min. resulting in a clearhomogeneous solution II. The solution II was cooled to about 37° C. andallowed to trickle into solution I over a period of about 3 min. withagitation. The temperature rose to a maximum of 68° C. during the next10 min. period of agitation. The resulting clear solution III had aviscosity of 214 cps. and a solids level of 50.0% as the orthoamic acid.The percent imidization was determined from a titration of thecarboxylic acid groups and found to be 1.2%.

To 270.0g. of solution III was injected, subsurfacewise and withagitation, a mixture of 93 ml. water and 18.5 ml. of 28% ammonia waterover a period of 2 min. The resulting solution IV was clear anddilutable with water. With agitation continued, a mixture of 23.4 g.n-butyl alcohol 2.2 g. N-methyl-2-pyrrolidone, 100 ml. water, andsufficient nonylphenolethylene oxide adduct to provide 60 p.p.m. in thetotal formulation, was added, resulting in a clear solution V having asolids level at 25.7% as a cured film. The solution had a viscosity of233 cps., a surface tension of 37.2 dynes/cm., and a pH of 7.0 at 24° C.

EXAMPLE 6

To a reactor equipped with a stirrer, nitrogen atmosphere, entry portand a thermometer well, was charged 108.1 g. N-methyl-2-pyrrolidonefollowed by 108.1 g (1.000 mole) m-phenylene diamine, resulting in aclear solution I. To a second, similar reactor equipped with a heatingmantle, was charged 241.0 g. N-methyl-2-pyrrolidone. The solvent washeated to 55° C. whereupon with agitation 241.0 g. (0.500 mole)4,4'-(2-acetoxy-1,3-glyceryl)bis-anhydrotrimellitate was charged over aperiod of 3 min. and stirring continued for an additional 10 min. periodduring which the temperature reached a maximum of 68° C. The solution IIwas cooled to about 30° C. and allowed to trickle into solution I withagitation over a period of 3 min. The temperature peaked at 65° C.during the additional 15 min. period of stirring. The resultinghomogeneous solution III in the reactor was allowed to cool to 35° C,whereupon with agitation a mixture of 200 ml. water and 67.0 ml. of 28%ammonia water was injected subsurfacewise over a period of 2.5 min.resulting in a clear solution IV. With agitation continuing a mixture of50.0 g. n-butyl alcohol, 4.0 g. N-methyl-2-pyrrolidone, 200 ml. water,and sufficient nonylphenolethylene oxide adduct to provide 45 p.p.m.,was added. The resulting clear solution V had a solids level of 29.0% asthe orthoamic acid in solution and 27.4% as a cured film. The solutionhad a viscosity of 175 cps., a surface tension of 36.8 dynes/cm., and apH of 7.1 at 24.5° C.

EXAMPLE 7

To the first of the reactors of the type referred to in Example 4 wascharged 132.2 g. N-formyl morpholine having a water content below 200p.p.m. The solvent was agitated and 132.2 g (0.667 mole) of4,4'-diaminodiphenyl methane (99% purity) was charged resulting in aclear solution I. To a second similar reactor equipped with a heatingmantle was charged 429.4 g. N-formyl morpholine having a water contentbelow 200 p.p.m. The solvent was agitated and heated to a temperature of58° C. whereupon 107.3 g. (0.333 mole) of3,3',4,4'-benzophenonetetracarboxylic dianhydride was charged over aperiod of 4 min. with agitation and the stirring continued for anadditional period of 15 min. After cooling to 28° C. the solution II ofdianhydride was trickled into the solution I in the first reactor withagitation over a period of 7 min. The stirring was continued for aperiod of about 15 min. The maximum temperature was 74° C. The resultingclear solution III was titrated for carboxylic acid and the percentimidization found to be 0.6%. The contents of the reactor were allowedto cool to 32° C. To the reactor was added 65.6 g. of a 60% aqueoussolution of isopropylamine, subsurfacewise and with agitation over aperiod of 2.5 min. resulting in a clear solution IV. To the reactor wasthen charged 42.0 g. of a mixture of 95% n-butyl alcohol and 5% N-formylmorpholine and sufficient nonylphenolethylene oxide adduct such that theresulting solution V was at 50 p.p.m. with respect to the nonionicsurfactant. The clear solution had a viscosity of 278 cps. at 25 C. anda solids level of 27.5% as the orthoamic acid and 26.1% as the curedfilm. The solution was water reducible.

Examples 8 through 10 represents the preparation of a series of resinsof the type M(AM)_(x) AM where X=1, X=3 and X=5, respectively, Mrepresents 4,4'-diaminodiphenyl methane and A represents4,4'-(2-acetocy-1,3-glyceryl)bis-anhydrotrimellitate. In comparison,Example 1 represents the resin where X=0.

EXAMPLE 8

To a reactor equipped with a stirrer, nitrogen atmosphere, entry port,and a thermometer well was charged 124.8 g. N-methyl-2-pyrrolidonehaving a water content below 200 p.p.m. The solvent was agitated and24.8 g. (0.125 mole) 4,4'-diaminodiphenyl methane (99% purity) wascharged over a period of about 30 sec. There resulted a clear solutionI. To the reactor was added a solution a 40.2 g. (0.0832 mole)4,4'-(2-acetoxy-1,3-glyceryl)bis-anhydrotrimellitate (99% purity) in40.2 g. N-methyl-2-pyrrolidone over a period of about 2 min. withagitation. Stirring was continued for another 10 min. resulting in aclear homogeneous solution II having a solids level of 28.3% as theorthoamic acid. The percent imidization was found to be 0.4. Thisprovided a molar ratio of M/A≅3/2 and an average structure of M(AM)_(x)AM where X=1. To the contents of the reactor was added, subsurfacewiseand with agitation, 11.4 ml. of 28% ammonia water over a period of 2min. The resulting solution III was clear and dilutable with water. Withagitation continuing, a mixture of 4.3 g. ethylene glycol n-butyl ether,1.7 g. N-methyl-2-pyrrolidone, 26.0 g. water, 13.2 g. n-butyl alcoholand sufficient nonylphenolethylene oxide adduct to result ultimately in45 p.p.m. was added resulting in a clear solution IV having a solidslevel of 22.8% as the orthoamic acid and 21.7% as the cured film (seeExample 1). The solution had a viscosity of 32 cps., surface tension of41.5 dynes/cm. and a pH of 7.2 at 24° C.

EXAMPLE 9

To the reactor of Example 8 was charged 120.7 g. N-methyl-2-pyrrolidone.The solvent was agitated and 20.7 g. (0.104 mole) 4,4'-diaminodiphenylmethane was charged over a period of about 30 sec. There resulted aclear solution I. To the reactor was added a solution of 40.2 g. (0.0832mole) 4,4'-(2-acetoxy-1,3-glyceryl) bis-anhydrotrimellitate in 40.2 g.N-methyl-2-pyrrolidone, over a period of about 2 min. with agitation.Stirring was continued for another 10 min. resulting in a clearhomogeneous solution II having a solids level of 27.4% as the orthoamicacid. The percent imidization was found to be 0.4%. This provided amolar ratio of M/A≅5/4 and an average structure of M(AM)_(x) AM whereX=3. To the contents of the reactor was added, subsurfacewise and withagitation, 11.4 ml. of 28% ammonia water over a period of 2 min. Theresulting solution III was clear and dilutable with water. Withagitation continuing a mixture of 4.3 g. ethylene glycol n-butyl ether,1.7 g. N-methyl-2-pyrrolidone, 26.0 g. water, 13.2 g. n-butyl alcoholand sufficient nonylphenolethylene oxide adduct to result ultimately in45 p.p.m. was added resulting in a clear solution IV having a solidslevel of 22.0% as the orthoamic acid and 21.0% as the cured film. Thesolution had a viscosity of 30 cps., surface tension of 40.5 dynes/cm.and a pH of 7.0 at 24° C.

EXAMPLE 10

To the reactor of Example 8 was charged 119.3 g. N-methyl-2-pyrrolidone.The solvent was agitated and 19.3 g. (0.0975 mole) 4,4'-diaminodiphenylmethane was charged over a period of about 30 sec. There resulted aclear solution I. To the reactor was added a solution of 40.2 g. (0.0832mole) 4,4'-(2-acetocy-of glyceryl) bis-anhydrotrimellitate in 40.2 g.N-methyl-2-pyrrolidone, over a period of about 2 min. with agitation.Stirring was continued for another 10 min. resulting in a clearhomogeneous solution II having a solids level of 27.2% as the orthoamicacid. The percent imidization was found to be 0.5%. This provided amolar ratio of M/A≅7/6 and an average structure of M(AM)_(x) AM whereX=5. To the contents of the reactor was added, subsurfacewise and withagitation, 11.4 ml. pf 28% ammonia water over a period of 2 min. Theresulting solution III was clear and dilutable with water. Withagitation containing a mixture of 4.3 g. ethylene glycol n-butyl ether,1.7 g. N-methyl-2-pyrrolidone, 26.0 g. water, 13.2 g. n-butyl alcoholand sufficient nonylphenolethylene oxide adduct to result ultimately in45 p.p.m., was added resulting in a clear solution IV having a solidslevel of 22.8% as the orthoamic acid and 21.7% as the cured film. Thesolution had a viscosity of 30 cps., surface tension of 40.7 dynes/cm.and a pH of 7.0 at 24° C.

Examples 11 through 13 represent the preparation of a series of resinsof the type M(BM)_(x) BM where X=1, X=3 and X=5, respectively, Mrepresents 4,4'-diaminodiphenyl methane and B represents 3,3',4,4'-benzophenonetetracarboxylic dianhydride. In comparison, Example 3represents this resin where X=0 and Example 23 below where X is inexcess of 20.

EXAMPLE 11

To the reactor of Example 8 was charged 100.0 g. of a 50.0% by weightsolution of 4,4'-diaminodiphenyl methane (0.242 mole) inN-methyl-2-pyrrolidone resulting in solution I. To the reactor wasadded, slowly, over a period of about 2 min. with agitation, 471.0 g. ofa 11.5% by weight solution of 3,3',4,4'-benzophenonetetracarboxylicdianhydride (0.168 mole) in N-methyl-2-pyrrolidone. Stirring wascontinued for another 10 min., resulting in a clear homogeneous solutionII having a solids level of 18.2% as the orthoamic acid. The percentimidization was found to be 0.3%. This provided a molar ratio of M/B≅3/2and an average structure of M(BM)_(x) BM where X=1. To the contents ofthe reactor was added, subsurfacewise and with agitation, 23.1 ml. of28% ammonia water over a period of 2 min. The resulting solution III wasclear and dilutable with water and at a solids level of 17.6% as theorthamic acid and 16.6% as the cured film. The solution had a viscosityof 40 cps., surface tension of 45.1 dynes/cm. and a pH of 8.2 at 24° C.

EXAMPLE 12

To a reactor of Example 8 was charged 100.0 g. of a 50.0% by weightsolution of 4,4'-diaminodiphenyl methane (0.252 mole) inN-methyl-2-pyrrolidone resulting in solution I. To the reactor wasadded, slowly, over a period of about 2 min. with agitation 565.3 g. ofa 11.5% by weight solution of 3,3',4,4'-benzophenonetetracarboxylicdianhydride (0.202 mole) in N-methyl-2-pyrrolidone. Stirring wascontinued for another 10 min. resulting in a clear homogeneous solutionII having a solids level of 17.3% as the orthoamic acid. The percentimidization was found to be 0.5%. This provided a molar ratio of M/B≅5/4and an average structure of M(BM)_(x) BM where X=3. To the contents ofthe reactor was added, subsurfacewise and with agitation, 27.7 ml. 28%ammonia water over a period of 2 min. The resulting solution III wasclear and dilutable with water and at a solids level of 16.7% as theorthoamic acid and 15.6% as the cured film. The solution had a viscosityof 46 cps., surface tension of 44.4 dynes/cm. and a pH of 8.0 at 24° C.

EXAMPLE 13

To the reactor of Example 8 was charged 100.0 g. of a 50.0% by weightsolution of 4,4'-diaminodiphenyl methane (0.252 mole) inN-methyl-2-pyrrolidone resulting in solution I. To the reactor wasadded, slowly, over a period of about 2 min. with agitation 605.6 g. ofa 11.5% by weight solution of 3,3',4,4'-benzophenonetetracarboxylicdianhydride (0.216 mole) in N-methyl-2-pyrrolidone. Stirring wascontinued for another 10 min. resulting in a clear homogeneous solutionII having a solids level of 16.9% as the orthoamic acid. The percentimidization was found to be 0.4%. This provided a molar ratio of M/B≅7/6and an average structure of M(BM)_(x) BM where X=5. To the contents ofthe reactor was added, subsurfacewise and with agitation, 29.7 ml. 28%ammonia water over a period of 2 min. The resulting solution III wasclear and dilutable with water and at a solids level of 16.3% as theorthoamic acid and 15.2% as the cured film. The solution had a viscosityof 40 cps., surface tension of 44.5 dynes/cm., and a pH of 8.0 at 24° C.

EXAMPLE 14

To a reactor equipped with heating mantel, nitrogen sparge, stirrer andthermometer, was charged 225.0 g. (2.160 mole) neopentyl glycol. Theheat was turned on and at about 100° C. after the neopentyl glycol wasliquified, 185.0 g. (0.963 mole) of trimelletic anhydride was added overa period of about 3 min. The mixture was held at 100° C. for about 10min. whereupon the mixture was clear. The temperature was raised to 170°C., and 95.0 g. (0.650 mole) of adipic acid was added. The reactor washeld at this temperature with read-outs of the acid number every hour.After about 5 hrs. at this temperature, an acid number of 56 wasobtained. The acid number was determined in acetone rather than theconventional benzene-ethanol solution since this resin is insoluble inthe latter. To this resin system was added 8.3% dimethylethanol aminemade up as a solution in water/t-butyl alcohol = 85/15, such that theresin solids level was 33.6%. There resulted a slightly hazy solutionhaving a pH of 7.4 and a viscosity of 8700 cps at 25° C. The polymer inthis form was water reducible. The idealized structure for this polymerbefore the amine addition is as follows: ##STR12## When R representsneopentyl glycol.

EXAMPLE 15

To a reactor equipped with a heating mantel, nitrogen sparge, stirrerand thermometer, was charged 245.0 g. (3.219 moles) propylene glycolfollowed by 255.0 g. (1.327 moles) trimelletic anhydride and 65.0 g.(0.445 mole) adipic acid. The temperature was raised to 172° C. and heldat this temperature until the acid number dropped to about 56, whichoccurred in about 6 hrs. Since this resin was insoluble in theconventional benzene-ethanol solvent, the acid number was determined inacetone.

The resin system was cooled and trickled into an agitating solution ofabout 8.3% dimethylethanol amine in water such that the resultingsolution was at a solids level of 34.2% and a pH of 7.6. There resulteda slightly hazy solution with a viscosity of 9400 cps. at 25° C. Thepolymer in this form was water reducible. The idealized structure ofthis polymer, before the amine addition, is as follows: ##STR13## WhereR represents propylene glycol.

EXAMPLE 16

Using the reactor referred to in Example 15, the following charge wasemployed: 255.0 g. (2.829 moles) butylene glycol (1-3); 232.5 g. (1.210moles) trimelletic anhydride; and 60.0 g. (0.410 mole) adipic acid.Using a similar set of reaction conditions, there resulted after aprocess time of 6 hrs. at 172° C., an acid number of 55. The polymer wastreated with an aqueous solution of dimethylethanol amine in the samemanner as in Example 15, resulting in a slightly hazy, water reducible,solution having a viscosity of 9000 cps at 25° C. at 33.9% solids and apH of 7.4. The idealized structure is similar to that shown in Example15 with R representing butylene glycol.

EXAMPLE 17

Using the reactor referred to in Example 15, the following charge wasemployed: 275.0 g. (2.640 moles) neopentyl glycol was charged and heatedto 172° C.; with agitation, 217.5 g. (1.132 moles) trimelletic anhydridewas added and the temperature held for 12 min., resulting in a clearsolution; with temperature held at 171° C.; 55.0 g. (0.376 mole) adipicacid was added. The contents of the reactor were held for about 6 hrs.at 172° C. until an acid number of 55 was obtained. The polymer solutionwas cooled and treated with an aqueous solution of ammonia such that theresulting 34.2% solids solution had a pH of 7.4. The water reduciblesystem had a viscosity of 8100 cps. at 25° C. The idealized structure issimilar to that shown in Example 15 with R representing neopentylglycol.

EXAMPLE 18

To a reactor equipped with heating mantel, nitrogen sparge, stirrer andthermometer, was charged 166.1 g. (1.000 mole) of terephthalic acidfollowed by 96.0 g. (0.500 mole) trimelletic anhydride and 318.4 g.(3.000 moles) of diethylene glycol. The temperature was increased to200° C. and maintained for about 21/2 hrs. There resulted a clearsolution. An additional 96.0 g. (0.500 mole) of trimelletic anhydridewas then added to the hot solution with heating and agitation maintaineduntil an acid number of about 50 was attained. The 100% solids systemwas treated at about 60°-80° C., with warm water containing sufficientmethyldiethanolamine to result in a 34% solids solution having a pH of7.2, and a viscosity of 1315 cps. at 25° C. The resulting polymersolution was water reducible and was observed to be stable for timeperiods in excess of three months.

EXAMPLE 19

To the reactor described in Example 18 there was charged 384.2 g. (2.000moles) of trimelletic anhydride (TMA) and 319.4 g. (3.000 moles) ofdiethylene glycol. The temperature was increased to 195° C. andmaintained for about 31/2 hrs., resulting in a clear solution of fusedpolymer having an acid number of about 53. After treatment withmethyldiethanol amine and water to 34% solids, the polymer solution wasslightly hazy, had a pH of 7.4 and a viscosity of 70 cps. at 25° C. Theresulting polymer solution was water reducible and stable for timeperiods in excess of three months.

EXAMPLE 20

To a reactor equipped with heating mantel, nitrogen sparge, stirrer andthermometer, was charged 222.8 g. (2.140 moles) neopentyl glycol. Thetemperature was raised to 173° C. To the fused glycol, under nitrogen,with stirring and with the temperature controlled at 173° C., was added130.6 g. (0.500 mole) tris(2-hydroxyethyl) isocyanurate. To the reactorthen was charged 217.5 g. (1.132 moles) trimellitic anhydride and thetemperature held for about 15 min., resulting in a clear solution towhich was added 55.0 g. (0.376 mole) adipic acid. The contents of thereactor were held at 173° C. for about 6.5 hrs. until an acid number of58 was obtained. The polymer solution was then treated with an aqueoussolution of dimethylethanol amine. The resulting slightly hazy waterreducible solution had a solids level of 34.5%, a pH of 7.8 and aviscosity of 5900 cps. at 25° C.

EXAMPLE 21

To a reactor equipped with a heating mantel, nitrogen sparge, stirrerand thermometer, was charged 245.0 g. (3.219 moles) propylene glycol,followed by 255.0 g. (1.327 moles) trimellitic anhydride, and 73.9 g.(0.445 mole) isophthalic acid. The temperature was raised to 170° C. andheld for a total of about 6.5 hrs. resulting in a clear resin having anacid number of 62, forming polyester system I. The resin system I wascooled and trickled into an agitating solution of about 8.3%dimethylethanol amine in water, so that the resulting solution was at asolids level of 33.6% and a pH of 7.8. The slightly hazy solution had aviscosity of 3700 cps. at 25° C. The polymer in this form was waterreducible. The idealized structure of this polymer is about as shown inExample 15, differing in that the aliphatic (CH₂)₄ group would bereplaced by the aromatic (C₆ H₄) group.

EXAMPLE 22

The synthesis of Example 21 was repeated except that instead of using0.445 mole of isophthalic acid, there was added a mixture of 43.8 g.(0.300 mole) of isophthalic acid and 84.4 g. (0.145 mole) of thereaction product of 2 moles of trimelletic anhydride and one mole of4,4'-methylene dianiline having the structure ##STR14## and a calculatedmolecular weight of 582.4. The temperature was raised to 174° C. andheld for about 7.5 hrs., resulting in a polymer having an acid number of66. The resin system was cooled and trickled into an agitating solutionof about 8.3% dimethylethanol amine in water so that the resultingsolution had a solids level of 34.2% and a pH of 7.4. The slightly hazysolution had a viscosity of 7400 cps at 25° C. The polymer in this formwas water reducible.

It is very evident that the number of useful water reducible polyestersis substantially unlimited. It is not the purpose of this presentationto show how many kinds of polyesters can be made, but to show theunexpected finding that an imide forming orthoamic acid amine has beenidentified that is fully compatible with water soluble polyesters. Highmolecular weight polyamides are well established and are also well knownto be costly. The combination of water soluble high molecular weightpolyamide acids with water soluble polyesters was futile as is evidencedin Example 23. However, the combination with an orthoamic acid diamineprepared according to Examples 1 -13 was unexpectedly found to result incompatible solutions and thermally very stable cured resin systems,which had surprisingly good electrical properties.

EXAMPLE 23

A Regal mixer equipped with cooling to the jacket was flushed with drynitrogen, dewpoint -65° C. and charged with 3760 g. of dryN-methyl-2-pyrrolidone (<0.01% water), followed by 360 g. (1.818 moles)p,p' -methylene dianiline, (>99.7% purity). After stirring for about oneminute, 293 g. (0.909 mole) 3,3',4,4'-benzophenonetetracarboxylicdianhydride, (>99.5% purity), was added with stirring over a period of 5minutes and the stirring continued for 15 minutes. The maximumtemperature during this period was 35° C. The temperature was reduced to25° C. and 299 g. (0.927 mole) of 3,3',4,4'-benzophenonetetracarboxylicdianhydride was added dropwise over a period of 15 min. with agitationand with the exotherm temperature rise controlled at a max. of 40° C.The resulting polyorthoamic acid solution was clear and had a solidscontent of 20.2%. The carboxylic acid content was determined bytitration with t-butylammonium hydroxide in pyridine to a thymol blueend point and the percent imidization calculated to be 0.6 ± 0.5%, oressentially a negligible amount. The inherent viscosity was determinedin N-methyl-2-pyrrolidone at 37.8° C. and found to be 0.60 dl./g. at C =0.500 g./dl. The kinematic viscosity of the system was 2400 cps at 40°C.

To the reactor was added, continuously, dropwise, and with agitation,over a period of 15 min., a solution of 3.6 g. (0.018 mole) ofp,p'-methylene dianiline in 100 g. of N-methyl-2-pyrrolidone and themixing continued under nitrogen and with cooling and with thetemperature mained at about 40° C. After an additional 45 min. of mixingthe kinematic viscosity was found to be 4700 cps at 40° C., and theinherent viscosity was 0.82 dl./g. After formation of the polymer, 200g. of conc. ammonium hydroxide was added to the Regal mixer with mixing.This was followed by addition of 600 g. of distilled water and thesystem stirred for about 30 min., resulting in a clear, aqueous based,polymer solution. The polymer system was treated with a flow controlagent by adding 0.6% by total system weight of a conventional nonionic,nonylphenolethylene oxide adduct. The resulting product was a clearsolution having a solids content of 17.2% and a viscosity of 480 cps at23.8° C. The solution was employed to coat copper wire in a conventionalwire enameling tower. The resulting 3.0 mil. build coating was found topass 25% elongation and lX flexibility.

EXAMPLE 24

To a reactor, equipped with a stirrer, was charged 120.0 g. of thepolyester as prepared in Example 14 at 33.6% solids. Over a period of2.0 min., 30.0 g. of the aqueous 17.2% solids polyorthoamic acid polymersolution prepared in Example 23 was added to the contents of thereactor. The stirrer was operated for an additional period of 15 min.This resulted in a polyester to polyorthoamic acid polymer resin ratioof about 9/1. Upon standing, a phase separation occurred, resulting in apolyorthoamic acid polymer rich layer at the top and a polyester richlayer at the bottom, indicating incompatibility of the polymer blend.

EXAMPLE 25-32

In a manner similar to that in Example 24 a series of polymer solutionblends were attempted using 120.0 g. of each of the polyesters preparedin Examples 15-22 with 30.0 g. of the aqueous 17.2 solids polyorthoamicacid polymer solutions prepared in Example 23 as follows:

    ______________________________________                                        Example 25                                                                             120.0   g. polyester of Example 15 + 30.0 g.                                          polymer solution of Example 23                               Example 26                                                                             120.0   g. polyester of Example 16 + 30.0 g.                                          polymer solution of Example 23.                              Example 27                                                                             120.0   g. polyester of Example 17 + 30.0 g.                                          polymer solution of Example 23.                              Example 28                                                                             120.0   g. polyester of Example 18 + 30.0 g.                                          polymer solution of Example 23.                              Example 29                                                                             120.0   g. polyester of Example 19 + 30.0 g.                                          polymer solution of Example 23.                              Example 30                                                                             120.0   g. polyester of Example 20 + 30.0 g.                                          polymer solution of Example 23.                              Example 31                                                                             120.0   g. polyester of Example 21 + 30.0 g.                                          polymer solution of Example 23.                              Example 32                                                                             120.0   g. polyester of Example 22 + 30.0 g.                                          polymer solution of Example 23.                              ______________________________________                                    

In each instance the polyester rejected the polyorthoamic acid polymer,resulting, in each instance, in a phase separation with formation of apolyorthoamic acid polymer rich layer and a polyester rich layer.

EXAMPLE 33

To a reactor, equipped with a stirrer, was charged 90.0 g. of an aqueous33.6% solids solution of a polyester as prepared in Example 21. Over aperiod of 2.0 min., 60.0 g. of an aqueous polyorthoamic acid polymersolution as prepared in Example 23, at 17.2% solids, was added to thecontents of the reactor. The stirrer was operated for an additionalperiod of 15 min. This resulted in a polyester to polyorthoamic acidpolymer resin ratio of about 75/25. On standing, a phase separationoccurred, resulting in a polyorthoamic acid polymer rich layer at thetop and a polyester rich layer at the bottom, indicating incompatibilityof the polymer blend.

EXAMPLE 34

To a reactor, equipped with a stirrer, was charged 135.0 g. of the 33.6%solids polyester solution as prepared in Example 21. Over a period of2.0 min., 15.0 g. of the polyorthoamic acid polymer solution as preparedin Example 23, at 17.2% solids, was added to the contents of thereactor. The stirrer was operated for an additional period of 15 min.This resulted in a polyester to polyorthoamic acid polymer resin ratioof about 95/5. On standing, a phase separation occurred, resulting inpolyester and a polyorthoamic acid polymer resin rich regions,indicating the tolerance of the polyester polymer for polyorthoamic acidpolymer is apparently well below 5%.

EXAMPLE 35

To a reactor equipped with a stirrer was charged 180.0 g. of an aqueoussolution of a polyester at 33.6% solids prepared according to Example 21followed by 18.8 g. of the aqueous solution of the orthoamic acidprepared by the procedure described in Example 1 at 36.0% solids (as thecured film). Stirring was continued for a period of 15 min. The resincured weight ratio of polyester to orthoamic acid diamine was at about 9to 1. In sharp contrast to the result obtained in Example 24, thereresulted a clear solution with no evidence of phase separation. To thereactor, with agitation, was added 10.0 g. of a mixture of 9.5 g.n-butyl alcohol and 0.5 g. N-methyl-2pyrrolidone containing a sufficientamount of nonylphenolethylene oxide adduct such that the resultingsystem had about 60 p.p.m. of the latter component. The resulting clearaqueous solution of the polymer blend had a solids level of 32.2%, asurface tension of 36.5 dynes/cm., a pH of 7.5 and a viscosity of 347cps. at 24° C. The solvent in this system is in excess of 80% water.About 0.5 g. of the solution was placed in an aluminum dish about 5.5cm. in diameter. The solution flowed out evenly. The sample was placedin a forced-air oven set at 150° C. for 15 min. and then removed andexamined. It was found to be a homogeneous clear film free of any phaseseparation. The cure was continued for 90 min. at 220° C. followed by 20min. at 250° C. There resulted a clear, tough 0.3-1.0 mil filmexhibiting excellent adhesion to and flexibility on the aluminumsubstrate. Another portion of the solution was placed on a coppersubstrate and another on an iron substrate and a doctor blade employedto draw uniform wet films. A similar cure schedule was employed and theresulting 0.2-0.5 mil films were found to be clear, tough, andexhibiting excellent adhesion to the substrates as evidenced by noseparation at the interface following considerable flexing.

The 32.2% solids solution was employed to coat 18 AWG wires, 0.0403 inchcopper and aluminum wire, using a conventional set of six wire enamelmetering dies, namely, 0.043, 0.044, 0.044, 0.045, 0.045, and 0.046 inchdiameter opening. Each of the wet drawn enamel films was cured with theaid of forced-air ovens before the next layer of wet film was applied.The resulting films were smooth and concentric. The film build was 2.8to 3.0 mil on the diameter. A description of the mechanical, chemical,electrical and thermal test methods have been presented above. Themechanical properties of the film included: flexibility of 25% and 1X oncopper and 15 % and 1X on aluminium; repeated scrape 15-25 strokes;unidirectional scrape resistance 1020 g.; passed snap elongation. Thechemical properties of the film included: pass of 70/30 and 50/50solvent resistance test. The electrical properties of the film included:strength in excess of 2000 v./mil in twisted pair test. The thermalproperties of the film included: cut-through temperature (see tablebelow); 155° C. heat shock passed at 2X-3X; 175° C. heat aging passed3X.

The above coated six pass wire was overcoated with a conventional Nylonwire enamel, namely, a solution of 15% 6,6-Nylon dissolved in a 70/30cresylic acid/hydrocarbon solvent. This was accomplished with an 0.047inch diameter opening for the seventh pass. The wet drawn Nylon film wascured with the aid of forced-air ovens. The resulting film composite wassmooth. A slight improvement was found in the heat shock test, namely1X-2X; the other properties cited above were found to be essentiallyunchanged.

EXAMPLES 36-42

To a series of polymer blend solutions prepared by the proceduredescribed in Example 35, at 32.2% solids by weight, was addedorganometallic compounds known to be accelerators utilized in the curingof certain polyesters. The catalysts employed and their concentrationsare as follows (in each instance the percent values are expressed aspercent organometallic by weight of the resin solids):

    ______________________________________                                        Example 36.                                                                              0.5% Tetraoctylene glycol titanate                                            (Tyzor OG)                                                         Example 37.                                                                              1.0% Tetraoctylene glycol titanate                                            (Tyzor OG)                                                         Example 38.                                                                              0.5% Triethanolamine titanate                                                 (Tyzor TE)                                                         Example 39.                                                                              1.0% Triethanolamine titanate                                                 (Tyzor TE)                                                         Example 40.                                                                              2.0% Triethanolamine titanate                                                 (Tyzor TE)                                                         Example 41.                                                                              0.5% Ammonium salt of titanium lactate                                        (Tyzor LA)                                                         Example 42.                                                                              2.0% Ammonium salt of titanium lactate                                        (Tyzor LA)                                                         ______________________________________                                    

These titanium chelates are commercially available from E. I. duPontdeNemours and Co. as follows: Tyzor OG at 100% solids; Tyzor TE as 80%solids in isopropanol; Tyzor LA as 50% solids in water. In each instancethe accelerator was compatible, forming stable, clear solutions with theExample 35 polymer blend solution. In order to evaluate the effect ofacceleration on the cure, a cut-through test was performed on filmscured out employing a standard cure schedule. The cut-through testinvolved formation of a 3.0 mil film on an aluminum substrate which wasthen shaped over an insulated copper wire and over which was thencrossed a bare copper wire, perpendicular to the coated substrate. A1000 g. weight was placed at the cross point and the unit placed in aforced-air oven. The oven was equipped with thermocouples and a rate oftemperature rise of 3°/min. With the aid of a multipoint recorder thecut-through temperature was automatically recorded as that point whenthe cured film was cut through and offered no resistance to flow ofcurrent. The cured film in each case was prepared by weighing 0.8 g.into a 5.5 cm. diameter aluminum dish and then subjected to a cureschedule of 15 min. at 150° C., 90 min. at 220° C. and 5 min at 255° C.There resulted clear, tough films exhibiting excellent adhesion toaluminum. The results of the cut-through test are presented in thefollowing table:

    ______________________________________                                        Sample      Catalyst     Cut-through                                          ______________________________________                                        Example 36                                                                              Tyzor OG - 0.5%   204                                               Example 37                                                                              Tyzor OG - 1.0%   220                                               Example 38                                                                              Tyzor TE - 0.5%   224                                               Example 39                                                                              Tyzor TE - 1.0%   253                                               Example 40                                                                              Tyzor TE - 2.0%   270+                                              Example 41                                                                              Tyzor LA - 0.5%   222                                               Example 42                                                                              Tyzor LA - 2.0%   270+                                              Example 35                                                                              No catalyst       184 (258*)                                        ______________________________________                                         *A cut-through of 258 was achieved when the time at 255° C. in the     cure schedule was extended from 5 min. to 50 min.                        

The 32.2% solids solution of Example 39 containing 1.0% triethanolaminetitanate (Tyzor TE) by resin weight, was employed to coat 18 AWG wire,0.0403 inch copper and aluminum wire using a conventional set of sixwire enamel metering dies and forced-air ovens to cure as described inExample 35. The resulting films were found to be smooth and concentricwith a 2.8 to 3.0 mil film build on the diameter. The properties of thefilm included: 25% and 1X flexibility on copper; 15% and 1X flexibilityon aluminum; repeated scrape 18-28 strokes; chemical resistance to 70/30and 50/50 solvent test; dielectric strength in excess of 2000 v./mil;2X-3X heat shock at 155° C.; 3X in the 175° C. heat aging.

From the above results of Examples 36 through 42, as compared to theresults of Example 35, it was apparent that the titanium chelateaccelerators offer desirable acceleration of the cure of coatingsapplied from the polyester orthoamic acid diamine aqueous solutionblends, without degradation of the film properties, and with an increasein cut-through temperature.

EXAMPLE 43

To a reactor equipped with a heating mantle and a stirrer and containing60.5 g. of the polyester resin system I of Example 21 at 60° C., wastrickled in over a period of 5 min. 14.1 g. of the orthoamic aciddiamine solution III of Example 1, at 50% solids at the orthoamic acidin N-methyl-2-pyrrolidone, with the reactor temperature controlled at60° C. and with agitation. The temperature was held at 50° C. withagitation continuing for an additional period of 10 min. There resulteda clear polymer blend solution at a solids level of 90% by weight inN-methyl-2-pyrrolidone (I). To the reactor was then added withagitation, continuously over a period of 3 min. a mixtutre of 9.92 g.dimethylethanol amine, 0.72 g. dimethyl amine, 111.7 g. water, 0.7 g.N-methyl-2-pyrrolidone, 10.9 g. n-butyl alcohol, 0.41 g. ethylene glycoln-butyl ether and sufficient nonylphenolethylene oxide adduct such thatthe resulting system had about 60 p.p.m. of the latter component. Thereresulted a clear solution with no evidence of phase separation. Thesolution properties of this polymer blend were as follows: Solids level,32.1%; surface tension, 36.7 dynes/cm.; pH, 7.6; viscosity 387 cps. at24° C. The solvent system is in excess of 80% water. These solutionproperties are not unlike those found for Example 35. The clarity,toughness, flexibility, and adhesion properties for films formed in amanner identical with the procedures cited in Example 35 wereessentially like those found for the alternative polymer blend method ofpreparation illustrated in Example 35. In essence a similar result canbe obtained independent of whether the polymer blending operation isperformed before or after the conversion of the separate polymers towater soluble polyelectrolytes. Additional studies indicate that thenormal heat-bodying of a resin-solvent system to provide a preferredsolids-viscosity relationship is best conducted on the resin blendbefore the resins have been converted to the water solublepolyelectrolyte form.

EXAMPLE 44

To a polymer blend solution prepared as described in Example 43, at asolids level of 32.1%, was added 1.0% triethanolamine titanate by weightof resin solids. There resulted a clear stable solution of about 32.1%solids, with solution properties similar to those cited in Example 43.About 0.8 g. of the solution was placed in an aluminum dish 5.5 cm. indiameter. The sample flowed out evenly and was cured using a stepwisecure of 15 min. at 150° C., 90 min. at 220° C., and 5 min. at 255° C.There resulted a clear, flexible, tough film exhibiting excellentadhesion to aluminum. A strip of coated aluminum containing 3.0 mil ofthe so-cured film was tested versus a similarly prepared film of Example43 in the cut-through apparatus described in Examples 36-42 and found tohave a cut-through of 256° C. as compared to a cut-through of 187° C.observed in Example 43. This example illustrates, as was found inExamples 36-42, that titanium chelates offer a desirable acceleration ofthe cure of the polyester-orthoamide acid diamine aqueous solutionblend.

EXAMPLE 45

To 74.6 g. of the polymer blend solution prepared according to Example43 solution I, at about 90% solids by weight, in N-methyl-2-pyrrolidone,was added 1% triethanolamine titanium chelate by weight of resin solidswith the polymer blend solution of about 55° C. with agitation and withagitation continuing for about 10 min. after the addition. To thereactor was then added, with agitation, continuously over a period of 3min., a mixture of 9.92 g. dimethylethanol amine, 0.72 g. dimethylamine,111.7 g. water, 0.7 g. N-methyl-2-pyrrolidone, 10.9 g. n-butyl alcohol,0.41 g. ethylene glycol n-butyl ether and sufficient nonylphenolethyleneoxide adduct such that the resulting system had about 60 p.p.m. of thelatter component. There resulted a clear stable solution at 32.1% solidswith solution properties similar to those cited in Examples 43 and 44.About 0.8 g. of the solution was placed in an aluminum dish 5.5 cm. indiameter. The sample flowed out evenly and was cured using a stepwisecure of 15 min. at 150° C., 90 min. at 220° C., and 5 min. at 255° C.There resulted a clear, flexible, tough film exhibiting excellentadhesion to the aluminum substrate. A strip of coated aluminumcontaining 3.0 mil of the so-cured film was tested in the cut-throughapparatus described in Examples 36-42 and found to have a cut-through of264° C. As was found in Examples 36-42, titanium chelates offer adesirable acceleration of the cure of the polyester orthoamic aciddiamine aqueous solution blends, and, furthermore, similar results canbe obtained independent of whether the polymer blending operation isperformed before or after the conversion of the separate polymers towater soluble polyelectrolytes. Additional studies indicate that thenormal heat-bodying of a resin-solvent system to provide a preferredsolids-viscosity relationship is best conducted on the resin blend withaccelerator included before the resins have been converted to the watersoluble polyelectrolyte form.

EXAMPLES 46-53

In a manner similar to that described in Example 35, a series of9/1=ester/orthoamic acid diamine solution blends were prepared using180.0 g. of each of the polyesters prepared as described in Examples14-22, at solids levels ranging from 33.9 to 34.6%, and 18.8 g. of theorthoamic acid diamine prepared as described in Example 1, at 36.0%solids (as the cured film) as follows:

    ______________________________________                                        Example 46.                                                                            180.0   g. polyester of Example 14 + 18.8 g.                                          orthoamic acid diamine of Example 1                          Example 47.                                                                            180.0   g. polyester of Example 15 + 18.8 g.                                          orthoamic acid diamine of Example 1                          Example 48.                                                                            180.0   g. polyester of Example 16 + 18.8 g.                                          orthoamic acid diamine of Example 1                          Example 49.                                                                            180.0   g. polyester of Example 17 + 18.8 g.                                          orthoamic acid diamine of Example 1                          Example 50.                                                                            180.0   g. polyester of Example 18 + 18.8 g.                                          orthoamic acid diamine of Example 1                          Example 51.                                                                            180.0   g. polyester of Example 19 + 18.8 g.                                          orthoamic acid diamine of Example 1                          Example 52.                                                                            180.0   g. polyester of Example 20 + 18.8 g.                                          orthoamic acid diamine of Example 1                          Example 53.                                                                            180.0   g. polyester of Example 22 + 18.8 g.                                          orthoamic acid diamine of Example 1                          ______________________________________                                    

In each instance, the polyester was compatible with the orthoamic aciddiamine, unlike the results found in Examples 24-34. In each instance,the blend was treated with a mixture of n-butyl alcohol,N-methyl-2-pyrrolidone, and the nonionic wetting agent as described inExample 35. The resulting clear solutions of polymer blends had a solidslevel ranging from 32 to 34%, a viscosity in the range of 260-480 cps.,a pH range of 7.4-7.8, a surface tension in the range of 36.4-37.5dynes/cm. and a solvent in the range of 80.0% by weight water. About 0.5g. of each solution was placed in an aluminum dish about 5.5 cm. indiameter. The solutions flowed out evenly. The samples were placed in aforced-air oven set at 150° C. for 15 min. and then removed andexamined. All films were found to be homogeneous, clear, and free of anyphase separation. The cure was continued for 90 min. at 220° C. followedby 20 min. at 250° C. There resulted clear, tough 0.3-1.0 mil filmsexhibiting excellent adhesion to and flexibility on the aluminumsubstrate in every case. Another portion of each solution was placed ona copper substrate and another on an iron substrate and a doctor bladeemployed to draw uniform wet films. A similar cure schedule was employedand the resulting 0.2-0.5 mil films were found to be clear, tough andexhibiting excellent adhesion to the substrate as evidenced by noseparation at the interface following considerable flexing in everycase.

EXAMPLE 54-56

In a manner similar to that employed in Example 35 a series of aqueouspolymer solution blends were attempted using 180.0 g. of the aqueous33.6 solids polyester solution prepared as described in Example 21, anda quantity of each of the aqueous orthoamic acid dimaine solutionprepared as described in Examples 2-5, such that the polyester toorthoamic acid diamine ratio was 9/1 by weight, as follows:

    ______________________________________                                        Example 54                                                                             180.0    g. polyester solution of Example 21 +                                         18.8 g. diamide-diacid-diamine solution                                       of Example 2.                                               Example 55                                                                             180.0    g. polyester solution of Example 21 +                                         27.8 g. diamide-diacid-diamine solution                                       of Example 4.                                               Example 56                                                                             180.0    g. polyester solution of Example 21 +                                         26.2 g. diamide-diacid-diamine solution                                       of Example 5.                                               ______________________________________                                    

In sharp contrast to the results of Examples 28-34 in which a phaseseparation was obtained with a polyorthoamic acid polymer rich layer anda polyester polymer rich layer, clear solutions were obtained in each ofExamples 54-56. Applying a cure schedule of 15 min. at 150° C., 90 min.at 220° C., 20 min. at 250° C. to about 0.5 g. of wet drawn film, thereresulted homogeneous clear, tough 0.3-1.0 mil films exhibiting excellentadhesion and flexibility on aluminum, iron and copper substrates.

EXAMPLE 57

To a reactor equipped with a stirrer was charged 180.0 g. of a polyesterat 33.6% solids prepared as described in Example 21 followed by 26.3 g.of the orthoamic acid diamine prepared as described in Example 3 at25.6% solids (as the imide). Stirring was continued for a period of 15min. The resin ratio of polyester to orthoamic acid diamine was at about9/1. In sharp contrast to the result of Example 24 there resulted aclear solution with no evidence of phase separation. To the reactor withagitation was added 10.0 g. of a mixture of 9.5 g. n-butyl alcohol and0.5 g. N-methyl-2-pyrrolidone containing a sufficient amount ofnonylphenolethylene oxide adduct such that the resulting system hadabout 60 p.p.m. of the latter component. The resulting clear highlyaqueous solution of the polymer blend had a solids level of 30.1%, asurface tension of 36.2 dynes/cm., a pH of 7.3 and a viscosity of 323cps. at 24° C. The solvent in this system was in excess of 77% water.About 0.5 g. of the solution was placed in an aluminum dish about 5.5cm. in diameter. The solution flowed out evenly. The sample was given acure schedule of 150° C. for 15 min., 90 min. at 220° C., and 20 min. at250° C. There resulted a clear, tough 0.3-1.0 mil film, exhibitingexcellent adhesion to and flexibility on the aluminum substrate. Anotherportion of the solution was placed on a copper substrate and another onan iron substrate and a doctor blade employed to draw uniform wet films.A similar cure schedule was employed and the resulting 0.2-0.5 mil filmswere found to be clear, tough, and exhibiting excellent adhesion to thesubstrates as evidenced by no separation at the interface followingconsiderable flexing.

The 31.1% solids solution was employed to cost 18 AWG wire, 0.0403 inch,copper and aluminum, using a conventional set of six wire enamelmetering dies, namely, 0.043, 0.044, 0.044, 0.045, 0.045 and 0.046 inchdiameter opening. Each of the wet drawn films was cured with the aid offorced-air ovens before the next layer of wet film was applied. Theresulting films were smooth and concentric. The film build was 2.8 to3.0 mil on the diameter. A description of the mechanical, chemical,electrical and thermal test methods have been presented above.Properties of the film included: 25% and 1X flexibility on copper; 15%and 1X flexibility on aluminum; repeated scrape of 18-30 strokes;resistance to 70/30 and 50/50 solvent; greater than 2000 v./mil;dielectric strength; 2X-3X in 155° heat shock; 2X-3X in 175° C. heataging.

To the 31.1% solids polymer blend aqueous solution was added 1.0%triethanolamine titanium chelate by resin weight and the resulting clearsolution was used to coat 18 AWG wire, copper and aluminum, using theconventional set of six wire enamel metering dies and forced-air ovencure as cited above. The resulting films were smooth and concentric. Thefilm build was 2.8-3.0 mil on the diameter. Properties of the filmincluded 25% and 1X flexibility on copper; 15% and 1X flexibility onaluminum; repeated scrape of 17-31 strokes; resistance to 70/30 and50/50 solvent; dielectric strength in excess of 2000 v./mil; 2X-3X inthe 155° C. heat shock; 2X-3X in 175° C. heat aging. No degradation ofproperties by inclusion of the accelerator was observed.

The six pass coated wire was overcoated with a conventional nylon wireenamel, namely, a 15% 6,6-Nylon dissolved in 70/30 cresylicacid/hydrocarbon solvent. This was accomplished with an 0.047 inchdiameter die opening for the seventh pass. The wet drawn nylon film wascured with the aid of forced air ovens. The resulting film composite wassmooth. A slight improvement was found in the heat shock test, namely,1X-2X; the other properties cited above were found to be essentiallyunchanged.

EXAMPLE 58

To a reactor equipped with a stirrer was charged 100.0 g. of a polyesterat 33.6% solids prepared as described in Example 21 followed by 17.2 g.of the orthoamic acid diamine prepared as described in Example 8 at21.7% solids (as the cured film). Stirring was continued for a period of15 min. The resin ratio of polyester to orthoamic acid diamine was atabout 9/1. In sharp contrast to the result of Example 24, there resulteda clear solution with no evidence of phase separation. To the reactor,with agitation, was added 5.0 g. of a mixture of 4.5 g. n-butyl alcoholand 0.5 g. N-methyl-2-pyrrolidone containing a sufficient amount of anonylphenolethylene oxide adduct such that the resulting system hadabout 60 p.p.m. of the latter component. About 0.5 g. of the solutionwas placed in an aluminum dish about 5.5 cm. in diameter. The solutionflowed out evenly. The sample was placed in a forced-air oven set at150° C. for 15 min. and then removed and examined. It was found to be ahomogeneous clear film free of any phase separation. The cure wascontinued for 90 min. at 220° C. followed by 20 min. at 250° C. Thereresulted a clear, tough 0.3-1.0 mil film exhibiting excellent adhesionto and flexibility on the aluminum substrate. Another portion of thesolution was placed on a copper substrate and another on an ironsubstrate and a doctor blade employed to draw uniform wet films. Asimilar cure schedule was employed and the resulting 0.2-0.5 mil filmswere found to be clear, tough, and exhibiting excellent adhesion to thesubstrates as evidenced by no separation at the interface followingconsiderable flexing.

EXAMPLES 59-63

In a manner similar to that utilized in Example 58, a series of polymersolution blends were attempted using 100.0 g. of a polyester at 33.6%solids prepared as described in Example 21 and an appropriate amount ofthe orthoamic acid diamines described in Examples 9-13, in order toprovide a 9/1=polyester to orthoamic acid diamine blend as follows:

    ______________________________________                                        Example 59.                                                                            100.0   g. polyester of Example 21 + 17.8 g.                                          orthoamic acid diamine of Example 9.                         Example 60.                                                                            100.0   g. polyester of Example 21 + 17.2 g.                                          orthoamic acid diamine of Example 10.                        Example 61.                                                                            100.0   g. polyester of Example 21 + 22.5 g.                                          orthoamic acid diamine of Example 11.                        Example 62.                                                                            100.0   g. polyester of Example 21 + 23.9 g.                                          orthoamic acid diamine of Example 12.                        Example 63.                                                                            100.0   g. polyester of Example 21 + 24.5 g.                                          orthoamic acid diamine of Example 13.                        ______________________________________                                    

As in Example 58, and in sharp contrast to the results of Examples 24-34where phase separations occurred resulting in polyester-rich andpolyimide prepolymer-rich layers, clear solutions were obtained inExamples 58-63. As in Example 58, each of the solutions in Examples59-63 was treated with a mixture of n-butyl alcohol andN-methyl-2-pyrrolidone (at 5.0 g./100 g. polyester solution) and anonionic surfactant. Applying a cure schedule of 15 min. at 150° C., 90min. at 220° C., and 20 min. at 255° C. to wet drawn films, thereresulted homogeneous clear, tough 0.3-1.0 mil films exhibiting excellentadhesion and flexibility on aluminum, iron and copper substrates in allcases.

EXAMPLE 64

To the polymer blend of Example 59 and 30.5% solids, which in turnemployed the polyester of Example 21 and the M(AM)_(x) AM orthoamic aciddiamine of Example 9 where x=3, was added 1% triethanolamine titaniumchelate by weight of resin solids. About 0.8 g. was placed in analuminum dish 5.5 cm. in diameter. The sample flowed out evenly and wascured using a stepwise cure of 15 min. at 150° C., 90 min. at 220° C.,and 5 min. at 255° C. There resulted a clear, flexible, tough filmexhibiting excellent adhesion to the aluminum substrate. A strip ofcoated aluminum containing 3.0 mil of the cured film was tested andcompared to a similarly prepared film of Example 59 in the cut-throughapparatus described in Examples 36-42, and found to have a cut-throughof 249° C. as compared to a cut-through of 179° C. for Example 59 whereno accelerator was employed. When the time in the cure schedule forExample 59 was extended from 5 min. at 255° C. to 50 min. at 255° C.,the cut-through was 245° C. for Example 59.

The 30.5% solids solution with the 1.0% accelerator was employed to coat18 AWG wire, 0.0403 inch, copper and aluminum, using a conventional setof six wire enamel metering dies and cured with the aid of forced-airovens as described in Example 57. The resulting films were smooth andconcentric. The film build was 2.8-3.0 mil on the diameter. Propertiesof the film included: 25% and 1X flexibility on copper; 15% and 1Xflexibility on aluminum; 70/30 and 50/50 solvent resistance; greaterthan 2000 v./mil dielectric strength; 2X-3X 155° C. heat shock; 2X-3X175° C. heat aging.

The six pass coated wire was given a seventh "overcoat" treatment withconventional Nylon wire enamel as described in Example 57. Allproperties were found to be essentially unchanged with exception of heatshock which showed a slight improvement to 1X-2X.

EXAMPLE 65

To the polymer blend of Example 62 at 29.0% solids, which in turnemployed the polyester of Example 21 and the M(BM)_(x) BM of Example 12where x=3, was added 1% triethanolamine titanium chelate by weight ofresin solids. About 0.5 g. was placed in an aluminum dish 5.5 cm. indiameter. The sample flowed out evenly and was cured, using a stepwisecure of 15 min. at 150° C., 90 min. at 220° C., and 5 min. at 255° C.There resulted a clear, tough, flexible 0.2-0.8 mil film exhibitingexcellent adhesion to the aluminum substrate. With the aid of a doctorblade wet films were drawn on copper and iron substrates. A similar cureschedule was applied resulting in 0.2-0.5 mil clear films exhibitingexcellent adhesion to the substrates as evidenced by no separation atthe interface following considerable flexing. A 1.0 g. sample was placedin the aluminum dish and the above cure applied to form a 3.0 mil film.Using the cut-through apparatus described in Examples 36-42, the curedfilm was found to have a cut-through of 254° C. as compared to acut-through of 182° C. for a similarly prepared film of Example 62 whereno accelerator was employed. When the time in the cure schedule ofExample 62 was extended from 5 min. at 255° C. to 50 min. at 255° C.,the cut-through was 247° C. for Example 62.

The 29.0% solids solution with the 1.0% accelerator was employed to coat18 AWG wire, 0.0403 inch, copper and aluminum, using a conventional setof six wire enamel metering dies and cured with the aid of forced-airovens as described in Example 57. The resulting films were smooth andconcentric. The film build was 2.8-3.0 mil on the diameter. Propertiesof the film included: 25% and 1X elongation of copper; 15% and 1Xelongation on aluminum; 70/30 and 50/50 solvent resistance; dielectricstrength in excess of 2000 v./mil; 2X-3X 155° C. heat shock resistance;2X-3X performance in the 175° C. heat aging test.

EXAMPLE 66

To a reactor, equipped with a stirrer, was charged 180.0 g. of theaqueous orthoamic acid diamine solution prepared as described in Example1 at 36.0% solids (as the cured film), followed by 20.0 g. of an aqueous33.6% solids polyester solution prepared as described in Example 21.

Stirring was continued for a period of 15 min. The ratio of polyester toorthoamic acid diamine was at about 1/9 by weight. There resulted aclear solution with no evidence of phase separation. The solution wasmetered onto aluminum, iron and copper substrates with the aid of adoctor blade. The samples were placed in a forced-air oven set for acure schedule of 15 min. at 150° C., 90 min. at 220° C., and 60 min. at250° C. In each instance there resulted tough, clear 0.2-0.5 mil filmsexhibiting excellent adhesion and flexibility.

EXAMPLE 67

The procedure described in Example 66 was repeated with the exceptionthat an equal weight of the orthoamic acid diamine solution and of thepolyester were employed, resulting in a resin ratio of about one-to-oneby weight. There resulted a clear solution, with no evidence of phaseseparation. The same procedure of film formation and cure was employedon the three cited substrates. In each instance, there resulted tough,clear, films exhibiting excellent adhesion and flexibility.

EXAMPLE 68

To a reactor, equipped with a was charged 180.0 g. of the aqueous 33.6%solids polyester solution prepared as described in Example 21, followedby 16.0 g. of the aqueous 36.0% solids (cured) orthoamic acid diaminesolution prepared as described in Example 1. Stirring was continued fora period of 15 min. With stirring, 4.0 g. of a 35.0% solids aqueoussolution of a low viscosity, liquid, phenolic resin, commerciallyavailable as BRLA 2854 from Union Carbide Corporation, was added over aperiod of 2 min., and the stirring continued for another 15 min. Thereresulted a clear solution. The resulting solids ratio was about 90/2/8,i.e., polyester/phenolic/orthoamic acid diamine. The solution wasmetered onto aluminum, iron and copper substrates with the aid of adoctor blade. The samples were placed in forced-air ovens set for a cureschedule of 15 min. at 150° C., 90 min. at 220° C. and 60 min. at 250°C. There resulted clear, tough, 0.2-0.5 mil films exhibiting excellentadhesion and flexibility on all three substrates.

EXAMPLE 69

To a reactor, equipped with a stirrer was charged 180.0 g. of theaqueous 33.6% solids polyester solution prepared as described in Example21, followed by 10.0 g. of the aqueous 36.0% solids orthoamic aciddiamine solution prepared as described in Example 1. After about 15 min.of stirring, 10.0 g. of BRLA 2854 (see Example 68) was trickled in overa 2 min. period and stirring was continued for an additional 15 min.There resulted a clear solution with a solids ratio of about 90/5/5,i.e., polyester/phenolic/orthoamic acid diamine. With the aid of adoctor blade and following curing in forced-air ovens as described inExample 68, there resulted clear, tough, 0.2-0.5 mil films exhibitingexcellent adhesion and flexibility on aluminum, iron and copper.

EXAMPLE 70

To a reactor, equipped with a stirrer, was charged 180.0 g. of theaqueous, 33.6% solids polyester solution prepared as described inExample 21, followed by 16.0 g. of the aqueous 36.0% solids orthoamicacid diamine solution prepared as described in Example 1. Stirring wascontinued for a period of 15 min. With stirring, 4.0 g. of a 35.0%solids 80/20 aqueous alcoholic solution of a commercial grade ofhexamethoxymethylmelamine, aminoplast resin, such as Cymel 301 fromAmerican Cyanamid Company, was trickled in with stirring over a periodof 2 min. The stirring was continued for an additional 15 min. Theresulting resin solids ratio was about 90/2/8, i.e.,polyester/aminoplast/orthoamic acid diamine. With the aid of a doctorblade and following curing in the forced-air ovens as described inexample 68, there resulted clear, tough, 0.2-0.5 mil films exhibitingexcellent adhesion and flexibility on aluminum, iron and copper.

EXAMPLE 71

To a reactor equipped with a stirrer was charged 180.0 g. of thepolyester at 33.6% solids prepared as described in Example 15 followedby 10.0 g. of the orthoamic acid diamine prepared as described inExample 1 at 36.0% solids. After 15 min. of stirring, 10.0 g. of Cymel301 (see Example 70) was trickled in with stirring over 2 min. and thestirring continued for an additional 15 min. There resulted a clearsolution with a resin ratio of about 90/5/5, i.e.,polyester/aminoplast/orthoamic acid diamine. With the aid of a doctorblade and forced air ovens and a cure schedule as described in Example70, there resulted clear, tough 0.2-0.5 mil films exhibiting excellentadhesion and flexibility on aluminum, iron and copper.

EXAMPLE 72

To a reactor, equipped with a stirrer, was charged 180.0 g. of theaqueous 33.6% solids polyester solution prepared as described in Example21, followed by 16.0 g. of the aqueous 36.0% solids orthoamic aciddiamine solution prepared as described in Example 1. Stirring wascontinued for a period of 15 min. With stirring, 4.0 g. of a 35.0%solids water soluble epoxy resin, such as Araldite DP-630 fromCiba-Geigy Corporation, was trickled in, with stirring, over a period of2 min. The stirring was continued for an additional 15 min. Theresulting resin solids ratio was about 90/2/8, i.e.,polyester/expoly/orthoamic acid diamine. The solution was metered ontoaluminum, iron and copper substrates with the aid of a doctor blade. Thesamples were placed in forced-air ovens for a cure schedule of 15 min.at 150° C., 90 min. at 220° C. and 20 min. at 250° C. There resultedclear, tough, 0.2-0.5 mil films exhibiting excellent adhesion andflexibility on all three substrates.

EXAMPLE 73

To a reactor, equipped with a stirrer, was charged 180.0 g. of theaqueous 33.6% solids polyester solution prepared as described in Example21, followed by 10.0 g. of the aqueous 36.0% solids orthoamic aciddiamine solution prepared as described in Example 1. After 15 min. ofstirring, 10.0 g. of Araldite DP 630 epoxy was trickled in, withstirring, over 2 min., and the stirring continued for an additional 15min. There resulted a clear solution with a solids ratio of about90/5/5, i.e., polyester/epoxy/orthoamic acid diamine. With the aid of adoctor blade and following the forced-air oven cure schedule describedin Example 68, there resulted clear, tough, 0.2-0.5 mil films exhibitingexcellent adhesion and flexibility on aluminum, iron and copper.

EXAMPLE 74

To a reactor equipped with a stirrer was charged 180.0 g. of thepolyester at 33.6% solids prepared as described in Example 14, followedby 18.9 g. of the orthoamic acid diamine prepared as described inExample 3 at 28.4% solids (as the cured film). Stirring was continuedfor 15 min. With stirring, 3.84 g. of a 35.0% solids aqueous solution ofa low viscosity liquid phenolic resin, commercially available as BRL1031 from Union Carbide Corporation, was added over a period of 2 min.,and the stirring continued for another 15 min. The resultinghomogeneous, clear, solution had a resin ratio ofpolyester/phenolic/orthoamic acid diamine of about 90/2/8. To thereactor, with agitation, was added 10.0 g. of a mixture of 9.5 g.n-butyl alcohol and 0.5 g. N-methyl-2-pyrrolidone containing asufficient amount of nonylphenolethylene oxide adduct such that theresulting system had about 60 p.p.m. of the latter component. Theresulting clear aqueous solution of the polymer blend had a solids levelof 31.6%, a surface tension of 36.2 dynes/cm., a pH of 7.4 and aviscosity of 377 cps. at 24° C. The solvent in this system was in excessof 80% water. The solution was metered onto aluminum, copper and ironsubstrates with the aid of a doctor blade. The samples were placed inforced-air ovens set for a cure schedule of 15 min. at 150° C., 90 min.at 220° C., and 20 min. at 250° C. There resulted clear, tough 0.2-0.5mil films exhibiting excellent adhesion and flexibility on all threesubstrates as evidenced by no separation at the interface followingconsiderable flexing.

The 31.6% solids solution was employed to coat 18 AWG wire, 0.0403 inch,copper and aluminum, using a conventional set of six wire enamelmetering dies and cured with the aid of forced-air ovens as described inExample 57. The resulting films were smooth and concentric, the filmbuild was 2.8 to 3.0 mil on the diameter. Properties of the filmincluded: 25% and 1X-2X flexibility on copper; 15% and 1X flexibility onaluminum; 70/30 and 50/50 solvent resistance; dielectric strength inexcess of 2000 v./mil; 2X-3X heat shock in the 155° C. test; 2X-3X inthe 175° C. heat aging test.

To the 31.6% solids polymer blend aqueous solution was added 1% ammoniumlactate titanium chelate by resin weight, and the resulting clearsolution was used to coat 18 AWG wire, copper and aluminum, using theconventional set of six wire enamel metering dies and forced-air ovencure as cited above. The resulting films were smooth and concentric. Thefilm build was 2.8-3.0 mil on the diameter. Properties of the filmincluded: 25% and 1X-2X flexibility on copper; 15% and 1X on aluminum;70/30 and 50/50 solvent resistance; dielectric strength in excess of2000 v./mil; 2X-3X 155° C. heat shock; 2X-3X 175° C. heat aging.

EXAMPLE 75

To a reactor equipped with a stirrer was charged 180.0 g. of thepolyester prepared as described in Example 17 at 34.2% solids followedby 21.0 g. of the orthoamic acid diamine prepared as described inExample 7 at 26.1% solids (as the cured film). After 15 min. ofadditional stirring, 3.91 g. of a 35.0% 80/20 aqueous alcoholic solutionof hexamethoxymethylmelamine, (Cymel 301, from American CyanamidCompany), was trickled in with stirring over a period of 2 min. Thestirring was continued for an additional 15 min. The resulting resinblend ratio was about 90/2/8, i.e., polyester/"aminoplast"/orthoamicacid diamine. To the reactor, with agitation, was added 10.0 g. of amixture of 9.5 g. n-butyl alcohol and 0.5 g. N-methyl-2-pyrrolidonecontaining a sufficient amount of nonylphenolethylene oxide adduct suchthat the resulting system had about 60 p.p.m. of the latter component.The resulting clear aqueous solution of the polymer blend had a solidslevel of 31.8%, a surface tension of 35.8 dynes/cm., a pH of 7.4 and aviscosity of 416 cps. at 24° C. The solvent in this system was in excessof 80% water. The solution was metered onto aluminum, copper and ironsubstrates with the aid of a doctor blade. The samples were placed inforced air ovens set for a cure schedule of 15 min. at 150° C., 90 min.at 220° C. and 20 min. at 250° C. There resulted clear, tough 0.2-0.5mil films exhibiting excellent adhesion and flexibility on all threesubstrates.

The 31.8% solids solution was employed to coat 18 AWG wire, 0.0403 inch,copper and aluminum, using a conventional set of six wire enamelmetering dies and cured with the aid of forced-air ovens as per Example57. The resulting films were at a 2.8-3.0 mil build on the diameter andwere found to be smooth and concentric. Properties of the film included:25% and 1X-2X flexibility on copper; 15% and 1X on aluminum; 70/30 and50/50 solvent resistance; greater than 2000 v./mil dielectric strengthin the twisted pair test; 2X-3X heat shock in the 155° C. test; 2X-3X inthe 175° C. heat aging test.

While certain illustrative embodiments and modifications of the presentinvention have been described in considerable detail, it should beunderstood that there is no intention to limit the invention to thespecific forms disclosed. On the contrary, the intention is to cover allembodiments, modification, alternatives, equivalents and uses fallingwithin the spirit and scope of the invention as expressed in theappended claims.

I claim as my invention:
 1. A coating composition for application to asubstrate from an aqueous solution comprising the admixture of a watersoluble film forming polyester resin and a water soluble aromaticoligorthoamic acid di-primary amine.
 2. An aqueous base resin coatingcomposition comprising, the admixture of a water soluble film formingpolyester resin and a water soluble aromatic digorthoamic aciddi-primary amine in the weight ratio of between about 0.1 and 10 partspolyester per part of diamine, said composition having a solids contentof between about 25% and 40% by weight, a coating of said composition ona substrate being curable upon the application of heat to form a curedresin coating on said substrate.
 3. A coating composition forapplication to a substrate from an aqueous solution comprising theadmixture of between about 1 and about 10 parts by weight of a watersoluble film forming polyester resin, and between about 1 and about 10parts by weight of a water soluble aromatic oligorthoamic aciddi-primary amine, a coating of said composition on a substrate beingheat curable to form a cured resin coating on said substrate.
 4. Thecoating composition defined in claim 3 wherein the admixture includes upto about 10 parts by weight of a water soluble phenol-formaldehyderesin.
 5. The coating composition defined in claim 3 wherein theadmixture further includes up to about 10 parts by weight of a watersoluble epoxy resin.
 6. THe coating composition defined in claim 3wherein the admixture further includes up to about 10 parts by weight ofa water soluble aminoplast resin.
 7. The coating composition defined inclaim 3 wherein said aromatic oligorthoamic acid di-primary amine is thereaction product of an aromatic diamine and an aromatic dianhydride inthe molar ratio of two-to-one respectively.
 8. The coating compositiondefined in claim 3 wherein said aromatic oligorthoamic acid di-primaryamine is a diamide diacid diamine.
 9. The coating composition defined inclaim 3 wherein said water soluble aromatic oligorthoamic aciddi-primary amine comprises the reaction product of an aromatic diamineand an aromatic dianhydride, in the molar ratio of m to m-1)respectively, where m has a value of from 2 to about 7, with theaddition to said reaction product of a volatile nitrogen containing basein an amount sufficient to make the reaction product water soluble. 10.The coating composition defined in claim 3 wherein said aromaticoligorthoamic acid di-primary amine is the reaction product of anaromatic diamine and an aromatic dianhydride in the molar ratio of m to(m-1) respectively, where m has a value of from 2 to about
 7. 11. Thecoating composition defined in claim 10 wherein said aromatic diamine isselected from the group consisting of:aromatic diamines having thegeneral formula:

    H.sub.2 N-R'-NH.sub.2

wherein R' is a divalent radical selected from the group consisting of##STR15##wherein R'" is an aryl group and "" is an alkyl or an arylgroup having 1 to 6 carbon atoms, n is an integer of from 1 to 4 and mhas a value of 0, 1 or more and ##STR16##wherein R" is selected from thegroup consisting of an alkylene chain having 1-3 carbon atoms,##STR17##wherein R'" and R"" are as above-defined and x is an integer ofat least
 0. 12. The coating composition defined in claim 10 wherein saidaromatic diamine is selected from the group consistingofp,p'-methylenedianiline p,p'-oxydianiline and m-phenylenediamine;andsaid aromatic dianhydride is selected from the group consisting of3,3',4,4'-benzophenonetetracarboxylic dianhydride,and4,4'-(2-acetoxy-1,3-glyceryl)-bis-anhydrotrimellitate.
 13. The coatingcomposition defined in claim 3 wherein said water soluble film formingpolyester comprises the reaction product of an aromatic acid oranhydride selected from the group consisting of trimellitic anhydride,trimellitic acid, terephthalic acid, isophthalic acid and mixturesthereof, and a polyhydroxyl selected from the group consisting ofneopentyl glycol, propylene glycol, butylene 1,3-glycol, diethyleneglycol, glycerine, trishydroxyethylisocyanurate, and mixtures thereof.14. The coating composition defined in claim 13 wherein said watersoluble film forming polyester further includes an aliphatic dibasicacid.
 15. A substrate having a coating thereon produced by applyingthereof a film of the composition defined in claim 3 followed by heatcuring of the film.
 16. A metal wire having a coating thereon producedby applying thereto a film of the composition defined in claim 3followed by heat curing of the film.
 17. A process for coating asubstrate comprising the steps of applying to said substrate a coatingof the composition defined in claim 3 and curing said coating.
 18. Aprocess for producing magnet wire comprising the steps of applying to awire a coating of the composition defined in claim 13 and curing saidcoating.
 19. A metal wire having a coating thereon produced by applyingthereto a film of the composition defined in claim 3 followed by heatcuring of the film and with a Nylon overcoating over said cured coating.20. A process for producing magnet wire comprising the steps of applyingto a wire a coating of the composition defined in claim 13, curing saidcoating, and applying a Nylon overcoating onto said cured coating. 21.The coating composition defined in claim 9 including the addition of anorganometallic accelerator.
 22. The composition of claim 21 wherein saidorganometallic accelerator is selected from the group consisting of thetitanium chelates.
 23. The coating composition defined in claim 9including the addition thereto of a flow control agent.
 24. Thecomposition of claim 23 wherein said flow control agent is selected fromthe group consisting of fluorocarbon surfactants, carboxypropylterminated dimethylsiloxane polymer flow agents,nonylphenoxypoly(ethyleneoxy)ethanol. and a mixture of cresylicacidphenol blend with n-butyl alcohol.
 25. A process for coating asubstrate comprising the steps of applying to said substrate a coatingof the composition defined in claim 21 and curing said coating.
 26. Aprocess for coating a substrate comprising the steps of applying to saidsubstrate a coating of the composition defined in claim 24 and curingsaid coating.
 27. A process for coating a substrate as defined in claim26 including the step of applying a Nylon overcoating to the curedcoating.
 28. A process for producing magnet wire comprising applying toa wire a coating of the composition defined in claim 12, curing saidcoating, and applying a Nylon overcoating to said cured coating.
 29. Thecoating composition of claim 12 including the addition of a flow controlagent and an organometallic curing accelerator.
 30. A process forproducing magnet wire comprising the steps of applying to a wire acoating of the composition defined in claim 29, curing said coating, andapplying a Nylon overcoating to said cured coating.
 31. Magnet wirecomprising a wire substrate having a coating thereon produced by theapplication and cure thereon of a coating of the composition defined inclaim
 29. 32. Magnet wire as defined in claim 31, including a Nylonovercoating.
 33. A coating composition for application to a substratefrom an aqueous solution comprising the admixture of between about 1 andabout 10 parts by weight of a water soluble polyester resin having anacid value of from about 45 to about 80 and a hydroxyl value of about100 to about 200; and between about 1 and about 10 parts by weight of awater soluble aromatic orthoamic acid diamine reaction product of anaromatic diamine and an aromatic dianhydride in the molar ratio of m to(m-1) respectively, where m has a value of from 2 to about 7; saidadmixture having an aromatic to aliphatic molar ratio of between about25 and about 50 percent aromatic; a coating of said composition on asubstrate being heat curable to form a cured resin coating on saidsubstrate.
 34. A process for coating a substrate comprising the steps ofapplying to said substrate a coating of the composition defined in claim33, and curing said coating.
 35. A process for producing magnet wirecomprising the steps of applying to a wire a coating composition asdefined in claim 33, curing said coating, and applying a Nylonovercoating to said cured coating.
 36. Magnet wire comprising a wiresubstrate having a coating thereon produced by the application and curethereon of a coating of the composition defined in claim
 33. 37. Magnetwire as defined in claim 36 including a Nylon overcoating.